Ultimate Fix-It-Yourself Manual--Appliance Repair Basics (Part 2)

Soldering and desoldering

Soldering is the technique of joining wires or other metallic surfaces with molten metal. Although twist- on wire connectors and crimp-on caps are commonly used to join appliance wires, soldering still plays an important role in repair work, especially to fasten wires to non-crimp-on terminals and in situations where vibration might loosen other connectors.

Soldering tools. To solder the fine wires found in small appliances, use a 25- to 50-watt soldering pen. Higher-wattage soldering guns and irons are more suitable for the heavier wiring of large appliances (some guns, however, feature high and low heat set tings and can be fitted with special tips for intricate work). The tip of any soldering tool must be kept tinned—coated with solder—to improve heat transfer and prevent pitting and tarnishing.

Solders and flux. The strongest solder for electrical work, and the easiest to use, is a mixture of 60 percent tin and 40 percent lead. (The high melting points of lead-free and silver solders make them inappropriate for most appliance repairs.) Before a joint is soldered, it must be coated with flux, a paste that removes tarnish and helps the solder penetrate the joint. Of the two kinds of flux available, use only rosin flux on wiring; acid flux corrodes copper. The best solder for most wiring jobs is rosin-core solder, a hollow wire of solder filled with rosin flux, which eliminates the need for a separate application of flux.

Applying and removing solder. Since solder always flows toward a heat source, it will penetrate a joint more effectively if you touch the iron to one side of the joint and the solder to the other. Before soldering, clean dirt or corrosion from the wires with fine-grit sandpaper or emery cloth. Twist or crimp the wires together to create a strong mechanical connection. If you need help holding the parts, place the iron in a soldering stand or the work in a soldering clamp (see Tips from the pros, above right). To avoid inhaling fumes, solder only in a well-ventilated area.

When removing large deposits of solder, use a de soldering pump. Small amounts of solder can be removed with desoldering braid.

Preparing a soldering iron:

1. Keep soldering-iron tip tinned at all times.

To tin the tip, unplug iron; file, scrape, or sand tip until bare metal shows through.

2.. Plug in iron and turn it to medium heat. Hold solder to tip until tip is coated. Wipe off excess solder with a damp sponge.

TIPS FROM THE PROS: Soldering clamps on weighted base steady the work and absorb heat that could damage delicate parts. Clamps also free one hand to hold solder.

Soldering and tinning techniques:

To tin a stranded wire, melt just enough solder to coat the strands evenly. Snip off any untinned strands of wire.

To solder a wire to a terminal, use just enough heat to melt the solder without causing it to sputter.

To solder wires, clean them with sandpaper, then twist together. Hold tip of iron to under side of joint; touch solder to wires from above.

How to desolder:

To desolder large areas, melt solder with a soldering iron (don’t overheat the work— you could damage parts). Press plunger of de soldering pump to suck up molten solder. Clean pump after use.

To remove small solder deposits, place desoldering braid between iron and solder: braid absorbs solder as it’s heated. Clean up flux residue with a foam swab soaked in denatured alcohol.

Cleaning and lubrication

Cleaning contacts and terminals:

Dirt, corrosion, and paint on electrical contacts and terminals inhibit conduction and are a major cause of appliance problems. Use an automotive-point file or emery paper to clean contacts and terminals. After cleaning, be sure to flush away any trace of dust or filings with electrical contact cleaner, an antistatic solvent that removes dirt and corrosion without damaging plastic. As with any solvent, avoid skin contact and don’t spray on hot surfaces. Some contact cleaners contain a light lubricant; don’t use them to clean wires prior to soldering.

Some switch contacts are made of soft silver for better conductivity. You can clean such contacts by sliding a piece of paper back and forth between them.

Faces of contacts on switch or thermostat should meet fully. Lightly tile or sand clean; flush away residue with contact cleaner.

Clean hard-to-reach connections with electrical contact cleaner from a can equipped with an extension nozzle.

Use steel wool to polish external contacts only; the loose particles and oily residue it leaves behind can damage internal parts.

Lubricants and lubricating:

Periodic lubrication will keep an appliance running smoothly and can solve many problems. When lubricating an appliance, carefully follow the directions in the service manual. Keep on hand a supply of commonly used lubricants such as SAE 20-weight non- detergent oil (for motors and bearings), lightweight machine oil (for everything from sewing machines to fishing reels), powdered graphite spray (for locks), penetrating oil (to loosen rusty fittings), and white lithium grease (for gears, hinges, and sprocket-and- chain mechanisms). Use only plastic-compatible lubricants on plastic parts. Most jobs require only a few drops of oil or a light coat of grease—too much lubricant can damage parts and attract dust and dirt.

Most gears need a light coat of grease on the top edges and around the teeth. Be careful not to coat nearby parts.

Some motors have a small oil cup (or a port covered with a plastic plug) for adding oil. Look for one on both ends of motor.

A telescoping-spout oiler makes it easy to reach hidden parts. Gently squeeze bottle to dispense oil. Don’t oil electrical connections.

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Repairing plastic parts:

A cracked housing or control knob can make it risky to operate an appliance, so be sure to repair damaged appliances without delay. Most nonmetallic appliance parts are made of ABS or polystyrene thermoplastic, for which epoxy is the best general-duty repair adhesive. For good results, parts should fit together tightly.

Light scratches can be polished out with white toothpaste (not gel). To polish deeper scratches and smooth mended cracks, rub the area lightly with fine sandpaper; then remove the sandpaper marks with fine steel wool.

Broken control-knob shafts can be mended if the break is clean and the parts fit closely. Apply epoxy; then assemble the pieces. Wrap the shaft tightly with nylon thread; then coat the windings with glue. The thread reinforces the repair.

To repair large parts, coat one broken edge with epoxy and squeeze the parts together for 1 mm. Then “bandage” the part at a right angle to the crack (pull the tape tight as you go). Let the part sit overnight before removing the tape.

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How motors work

In an electric motor, electricity flowing through bare wires called windings is used to generate magnetism, which in turn is used to rotate the motor shaft.

The magnetic field generated in this way is called electromagnetism. It has the same properties as ordinary magnetism—like poles repel each other and opposite poles attract—except that the poles can be reversed simply by reversing the direction of the electricity flowing through the windings.

The universal motor, so called because it will work on either alternating or direct current, is the most common type of motor in small appliances. All electric motors, however, have two features in common: a magnetized stationary component (called a stator or a field) and a rotating component (called a rotor or an armature). The rotor is also magnetized, either by direct application of current or by induction, a process in which current is created by the movement of the rotor within the stator’s magnetic field. Continually reversing the current generating one or both of these magnetic fields turns the rotor and thus the motor shaft.

A distinguishing feature of universal motors is that both the stator and the rotor have windings (often called coils). In contrast, DC motors have rotor windings --but usually no stator windings, and induction motors have stator windings but no rotor windings (see Types of motors). Universal motors also have two brushes and a commutator. The commutator is simply a series of brass bars insulated from each other; each bar is wired to the rotor windings Brushes, mounted on the motor frame, press against the commutator, conducting current to the rotor windings.

As each winding is activated, it sets up a magnetic field that interacts with the stator’s magnetic field to produce rotation.

QUICK FORMULAS - - Horsepower is the unit commonly used to describe a motor’s power.

Horsepower = amps x volts / 746

Inside a universal motor

• Stator windings
• Rotor winding
• Rotor
• Fan
• Motor shaft
• Bearing
• Housing
• Brush access cap
• Power cord

The moving parts of a universal motor are the motor shaft, fan, rotor, and commutator. Brush; Commutator; Brush holder

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FOR YOUR SAFETY:

If you suspect that a motor is faulty, shut it off before touching it or the appliance that houses it. If it has no plug, or if touching the plug may bring you in contact with water, turn off power to the circuit by tripping the circuit breaker or removing the fuse that controls it.

Disconnect any motor from its power source before servicing it. Never work on a motor in a damp or wet location. When performing tests requiring electricity, place the motor on a dry insulating surface such as a wood or rubber mat.

Discharge capacitors before servicing the motor. Capacitors store electricity and can deliver a shock even if the motor is unplugged.

Dry a wet electric motor before servicing or operating it. To dry a motor, place it in an oven set at the lowest temperature (no more than 150°F); leave it with the door open until the motor stops steaming.

When reinstalling a motor, make sure the grounding wire is connected before restoring power.

Before starting a motor, be sure belts and pulleys are fully secured. Keep hands, hair, clothing, and tools out of the way.

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Understanding a basic motor:

Magnetic field Magnetism. When suspended freely, magnets naturally align along the Earth’s magnetic north-south axis. Similar ends, or poles, of magnets repel each other; opposite poles attract.

Electromagnetism. Any electricity flowing through a wire creates a magnetic field around it. Wires placed close together strengthen the effect as each field overlaps adjoining fields.

Applying the concepts. An electro magnet can be created by wrapping current-carrying wire around an iron core. Reversing the direction of cur rent reverses the location of the poles.

Household electricity (60-cycle alternating current) reverses direction 120 times per second. An electromagnet’s poles will therefore change just as often once current begins to flow.

As the current changes direction, the bar magnet will spin constantly as its poles try to align with the constantly changing poles of the electromagnet. A gear harnesses this motion.

Types of motors:

Universal motor is found in many small appliances and power tools. Commutator has parallel brass bars, each wired to a separate rotor winding. As rotor turns, brushes carrying current press against commutator, individually energizing bars and corresponding rotor windings. Magnetic field at each winding interacts with magnetic field of stator to rotate shaft. Advantages: efficient; high torque (turning force) at low speeds; easy speed control. Disadvantages: rapid wear of parts, especially brushes.

Split-phase induction motor typically runs large appliances such as washing machines. Stator windings are “split.” One set, governed by centrifugal switch, provides starting torque (turning force); the other set controls operation after starting. Capacitor delivers specially timed charge to boost starting torque. Rotor is magnetized by moving within field windings: it receives no current from power supply. Internal circuit protects motor from damaging overloads. Advantages: reliability and low maintenance due to few moving parts. Disadvantages: poor variable-speed control: high current required for starting.

DC motor of the permanent-magnet (PM) type shown here often powers battery-operated appliances, tools, and toys. Design of a PM motor is similar to universal motor except that the stator consists of a permanent magnet instead of electrified windings. Current is supplied to the rotor only, via brushes. Some DC motors include a fan. Advantages: high power-to-size ratio and high torque at low speed. Disadvantages: poor performance at subfreezing temperatures; tendency to overheat under heavy load.

Shaded-pole induction motor typically powers such small appliances as can openers and hair dryers. Windings magnetize iron stator. Copper shading wire creates electrical imbalance that provides torque needed for starting. Advantages: low cost, small size, and extreme reliability. Disadvantages: low power and inability to reverse direction unless specially modified.

Starting a motor:

Universal and DC motors lack starting mechanisms because in both cases the stator and the rotor are magnetized as soon as the power supply is turned on. The resulting interaction between magnetic fields causes the rotor to spin. (In a universal motor, current magnetizes both stator windings and rotor windings. In a DC motor, current magnetizes rotor windings only; the stator itself is a permanent magnet.) Lacking rotor windings, induction motors require start windings or other devices to give the rotor an initial spin so that it becomes magnetized by induction.

A split-phase induction motor has two sets of stator windings—start windings and run windings—that are magnetized at different instants. These interacting magnetic fields give the rotor a starting spin. A capacitor connected to the start windings strengthens its field, helping to start the motor under load. Always discharge a capacitor before handling it.

Centrifugal switch on a split-phase motor pre vents start windings from burning out by cutting power to them when motor approaches top speed. Arms on a governor attached to the motor shaft swing outward as the shaft spins faster, eventually causing switch contacts to open, thereby cutting power to start windings. Switches may be outside the motor tor easy servicing.

On a shaded-pole induction motor, shading wire delays rate at which parts of the stator are magnetized by the stator windings. The delay is just enough to get rotor to move. Once in motion (and depending on load and voltage), rotor quickly gains speed. Because a typical shaded-pole motor lacks a capacitor, starting torque (turning force) is low; if overloaded, motor won’t start.

Controlling a motor’s speed:

Tapped field speed control is used to vary speeds in appliances that have several leads (taps) coming from the stator windings. Multi- speed switch allows power to be applied to any tap. Motor speeds are lowest when current flows through entire winding, highest when it flows through smallest segment.

Solid-state control is an electronic version of a governor. Key part is a silicon-controlled rectifier (5CR) that allows current to pass according to factory-set voltage. Speed is controlled as SCR clips” a portion of each cycle; the greater the clip, the slower the speed. Control is less prone than rheostat to heat buildup.

Governor is similar to a centrifugal switch. In type shown here, weighted scissor like device is linked to motor shaft. When shaft spins, centrifugal force pulls weights outward, causing actuator pin to push against contact arm. At high speed, pin opens contacts, cutting power to motor. When motor slows, power is restored.

Rheostat may control speed in older tools or appliances. It’s basically a wire coil that can be tapped at any point by means of a sliding contact. When wired into a motor circuit, a rheostat’s sliding contact provides a means of varying resistance. If resistance is high, current drops and so does motor speed.

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TIPS FROM THE PROS:

Before pulling out a volt-ohm meter to test a faulty motor, repair professionals generally gather information from a more immediate source: their own senses. You can do the same simply by paying attention to what the motor is trying to “tell” you as it operates.

If notice the motor and drive mechanisms while the appliance is running, look for gears and motor shafts that wobble, if only slightly. Worn bearings are the likely culprit, but a wobble could also indicate a misalignment of the moving parts. In either case, the problem will strain the motor and make the appliance noisy.

You can usually smell a faulty motor before serious damage is done. A mild odor of hot oil, metal, or plastic usually means that the motor is overheating, a problem often caused by overheated winding insulation or by friction in the motor bearings or drive components. Prompt lubrication may be all it takes to save the motor. But if the windings burn and short internally, the charred plastic insulation will emit a pungent acrid odor—a sure sign that the windings have to be replaced.

A motor too hot to touch is in trouble (a properly running motor will get warm but not hot). The air intakes may be clogged with lint or other debris, preventing the fan from drawing cool air over the windings. Excess heat also indicates an overworked motor—check to see if the gears are clogged, a belt is too tight, or the bearings are dry.

It you hear a grinding noise, suspect a worn-out bearing. A squealing noise, often intermit tent, means it’s time for lubrication. It’s normal to hear the “snap” of a centrifugal switch closing in a split-phase motor, but if the switch is bad (or if the motor overheats) you’ll hear the overload protector “click” as it shuts off the motor.

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Drive mechanisms:

Drive belts and gear assemblies put a motor’s power to work but also create much of the stress placed on the motor during operation. As a result, it’s sometimes these parts, not the motor, that cause problems in an appliance. Drive parts must be properly lubricated, adjusted, and aligned. Before disassembling, note their arrangement to ensure correct reassembly.

Direct-drive parts such as fan blades mount directly on the motor’s driveshaft, often by means of a collar that mates with a flattened portion of the shaft. Noisiness or vibration may indicate that the collar is loose. Tighten the setscrew with a hex key or screwdriver, but don’t overtighten. Don’t start motor until guard or shield is reinstalled around moving parts.

Pulleys and drive belts transfer power in large appliances such as washing machines and furnace blowers. Pulleys usually mount to motor and component shafts with pins (keys) and set screws. If belts are too tight, they can damage motor; if too loose, they can slip or fly off. Replace worn belts promptly. Don’t get oil on belts when lubricating motor or other parts.

Reduction gears, commonly found in electric tools and in appliances such as can openers, reduce the speed of a driveshaft to a speed below that of the motor itself, while increasing torque. Gears may come in pairs, and may have straight or helical-cut teeth. Examine gears for tooth damage and wear; replace them if necessary.

Worm gears change the direction in which drive- shaft power is applied. Such gearing can also be used to create multiple drive-shafts, as in the mixer shown above (note that the paired shafts rotate in opposing directions). One or more gears may be plastic to reduce noise; check them for damage or wear, and replace if necessary.

Motor disassembly:

Taking apart a small electric motor is fairly easy. Be sure, however, to note exactly how it comes apart so that you can readily put it back together again.

CAUTION: Disconnect the power source and discharge the capacitor before starting to disassemble a motor.

Start by removing anything attached to the motor shaft, including collars, pulleys, and fans (left). Carefully examine each part as you remove it, and look for distinguishing features that will serve as landmarks during reassembly. Use masking tape to label each part.

Most motor cases can be opened as shown at right. Once the case is open, however, what you will find depends on the type of motor. Usually the motor shaft and rotor (see Types of motors) can be pulled free after you remove the rear housing. In split-phase motors, part of the centrifugal switch will come out at the same time.

Keep a rag on hand to remove any grease or oil that may get on your fingers; these materials shouldn’t get on electrical connections, including the rotor and coils. Tag wires as you unfasten them, and be careful not to dislodge the brushes, which may spring loose before you can study their proper position. With the rotor removed, you can easily check the bearings for signs of wear. (Don’t remove any fibrous packing around the bearings—it serves as an oil reservoir near lubrication points.)

When you’re reassembling a motor, tighten body bolts evenly (a bit at a time) to prevent the shaft from binding. Turn the shaft periodically by hand to make sure that it moves freely.

1. Mark housings with felt-tip pen or awl to ensure precise reassembly. Make two sets of marks on one end, one set on the other, to avoid reinstalling center housing backward. All marks must straddle seams.

2. Use screwdriver and a wrench or nut driver to unfasten body bolts holding end housings in place. Most motors have four long bolts. Some have cover plates over one or both housings that must be removed to access body bolts.

3. Remove rear housing. If it fits tightly against main housing, tap lightly at several points around circumference with a hammer and cold chisel (not a woodworking chisel) or wood block. With housing off, internal parts will be accessible.

Cordless tools and appliances

Thanks to improved battery technology and the advent of powerful lightweight motors, a wide range of power tools, appliances, and electronic devices are now available in cordless models, the best of which nearly match the power and performance of their corded counterparts. Three features distinguish cord less appliances from corded models: a direct-current (DC) motor, rechargeable batteries, and a battery recharging unit.

Unlike corded appliances, which must be plugged into 120-volt alternating current (AC), cordless models go where they’re needed. Periodically, depending on the type and design of the appliance and how long it has been used, either the appliance or its detachable battery pack must be returned to the charger.

Cordless appliances and tools are subject to most of the same problems as their corded counterparts. If a problem is not due to a defect in the appliance or tool itself, the culprit is usually worn batteries or a defective charging unit. Techniques for testing and troubleshooting batteries and chargers are described on the facing page.

NiCad battery; Battery pack

Rechargeable batteries. Many cordless appliances operate on nickel-cadmium batteries (NiCads), either individual cells or a battery pack consisting of as many as 20 cells. Each cell provides direct current at about 1.2 volts, approximately the same as an AA penlight battery. Battery packs slip directly into the appliance or tool or have snap-on terminals. The wire leads of some battery packs (like those in cordless phones) are soldered to the appliance, circuitry. Don’t try to solder individual cells; overheating will damage them.

Although NiCads can be recharged up to 1,000 times before they wear out, undercharging them shortens their hfe. Read the package directions care fully before using a new cordless appliance, and make sure to charge NiCads fully.

When a rechargeable device tails, refer to the relevant troubleshooting chart for its corded equivalent. If you can’t locate the problem there, suspect worn batteries or a defective charger.

Cordless drill; Cordless shaver; Electric toothbrush; Cordless mixer; Cordless vacuum

Recharging units:

Recharging a battery involves two items: a transformer and a diode rectifier. The transformer steps voltage down from 120-volt household current to the much lower voltages required by rechargeable batteries. The ratings plate on the charger lists both input and output voltages. The rectifier, located either in the charger or in the appliance itself, converts AC cur rent to the DC current that batteries use. During the charging process some electricity is lost as heat, which is why chargers get warm as they operate.

How long it takes to recharge batteries depends both on their condition and on the amperage supplied by the charger. “Trickle” chargers, working at very low amperage, may take 14 to 16 hours to fully recharge a battery pack. Fast chargers, using much higher amperage, can do the job in as little as 15 minutes. To keep the batteries from overheating or even exploding, fast chargers include special sensing circuitry that prevents overheating. Always make sure that the charger you use is compatible with the appliance or battery pack.

Stand-type chargers connect directly to the appliance during charging. Electricity flows into the seated appliance through metal contacts or via an electromagnetic field that induces an electric charge (see facing page).

Battery-pack chargers turn tools and appliances into steady performers. While one battery pack is at work in the tool, a second or third can be charging so you never have to wait for fresh batteries. This is the preferred system for charging cordless power tools.

Recharging tips:

Use the proper charger. The charger supplied with a tool or appliance is the only one you should use to charge its batteries, even if the batteries fit other chargers. This ensures that the voltage and charging rate are correct for the batteries.

Don’t overcharge. Don’t store a battery pack or appliance in the charger base all the time unless the manufacturer’s instructions specifically recommend it.

Avoid short memory syndrome. If you recharge a NiCad before it’s fully discharged, it may start retaining its charge lot shorter and shorter periods. Before discarding a battery lack afflicted with short memory syndrome, try to restore Is memory: Operate the device until the battery is completely exhausted. Then recharge the battery pack fully.

Repeat this drain/charge cycle at least three times. If the battery pack still doesn’t return to full power, test the charger and battery (see right). New types of rechargeable batteries, more potent than NiCads and therefore not subject short memory syndrome, are increasingly being used in cordless equipment.

Testing charger units and batteries:

DC output charger (transformer and rectifier). Set a VOM on 25 DCV scale. Plug in charger and touch VOM probes to charger contacts. If meter reads zero, reverse the probes. Charger is OK if either reading is approximately 1 volt above the charger’s rated output.

Induction charger, the type usually used with electric toothbrushes and other oral hygiene devices, works without metal contacts to appliance or battery pack. To test, plug in power cord. Hold a steel knife blade against interior of charging well. Blade will vibrate if charger is working properly.

AC output charger (transformer only). Set a VOM on 25 ACV scale (be certain charger output is less than 25 volts before connecting to VOM). Touch probes to contacts. If no reading is obtained, the transformer is faulty. Don’t test chargers rated higher than 25 volts.

Battery pack. Pack should be fully charged for test. Set a VOM on the DCV range just above pack’s rated out put. Touch red VOM probe to the pack’s “+“ terminal and the black probe to the “—“ terminal. If reading is more than 1 volt below rated output, pack is bad and should be replaced.

Troubleshooting batteries and chargers

Problem:

Cordless appliance or tool doesn’t run, lacks power, or does not run long enough:

CAUSE? / Solution:

POWER OFF AT OUTLET? See General troubleshooting, . Also make sure that the outlet is not wired into a wall switch that has been turned off. The charger must be on continuously in order to keep the batteries fully charged.

POOR ELECTRICAL CONTACT? With the charger unplugged, clean the contacts between the power handle and the charger with an automotive-point file or emery paper. If the contacts are difficult to reach, try spraying them with electrical contact cleaner. To improve contact, rotate and slide the power unit in and out of the charger well several times.

DEFECTIVE CHARGER? Test the power cord (see General troubleshooting) and the charger (see tests above). Replace the power cord if it’s defective. If the charger test reveals a defect, take the charger to an authorized service center for repair or replace it. Most newer chargers cannot be repaired or are not worth repairing.

WORN OUT OR DEFECTIVE BATTERIES? If a cordless tool or appliance runs for shorter and shorter periods between re-chargings, the NiCad batteries are probably worn out. Do a visual check of the batteries or battery pack. Look for corroded terminals or a sticky substance (electrolyte) leaking from the battery. If you find electrolyte leaking, replace the battery pack (be sure to avoid skin contact with leaking electrolyte). If there is no leakage visible, test the battery pack (see above) and replace it if necessary. To avoid battery memory” problems in the first place, see Recharging tips, above.

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Environmental Hints:

Recycling batteries

Cadmium and other heavy metals used to make rechargeable batteries can pose a serious health hazard if released into groundwater or air. Long-term exposure to these metals may be linked to higher incidences of kidney disease, birth defects, and cancer.

Concern about the number of rechargeable batteries being sold has led many state and local governments to organize battery recycling programs. In some states it’s unlawful to dispose of rechargeable batteries in household trash. Instead, residents must recycle their rechargeable batteries through an established collection network. Selected retail outlets that sell cordless appliances and rechargeable batteries sometimes serve as drop-off points. Manufacturers may also accept batteries for recycling.

All rechargeable batteries should carry a logo like the one above. Below the logo will be a designation for the type of battery (“Ni-Cd” for nickel cadmium or “Pb” for lead).

If there’s no recycling program in your area, see if local tool and small-appliance retailers will accept rechargeables for recycling, or hold on to the batteries until a community recycling program has been established.

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General troubleshooting

Described here are the most common problems that afflict appliances—the appliance does not work, it repeatedly trips a cir cult breaker, or it shocks the user—as well as possible causes and solutions. This section has been designed to work with the appliance trouble shooting charts that appear in the rest of the book. In addition, the information in these pages will help you diagnose the common problems of nearly any appliance, even those that are not covered in this book.

First steps. Be fore you begin troubleshooting an appliance, check the owner’s manual to make sure you are using the device properly.

Don’t overlook the obvious. Is the appliance plugged in and turned on? Is it plugged into a switched receptacle whose switch is turned off? Have you been maintaining the appliance properly? Often, a few drops of oil in the right place is all it takes to restore a balky appliance. Once you’ve deter mined that an appliance is defective, check its warranty. If the appliance is still under warranty, let the manufacturer or an authorized service center do the repair. If you decide to handle a repair yourself, read this chapter carefully first; pay special attention to the pages entitled Getting started, Disassembly, and Wires, cords, and plugs. Then turn to the section of the guide devoted to the appliance in question. If you are new to appliance repair, bear in mind that even the most complicated procedure can be bro ken down into a logical sequence of simpler steps.

Finding problems.

Most appliance repairs fall into two broad categories: mechanical and electrical. Jammed gears, a broken drive belt, and other mechanical problems are relatively easy to locate with your eyes or ears. (For more on troubleshooting with your senses, see Tips from the pros While some electrical problems, such as dirty switch contacts, may be visible, most are not. Tracking them down often requires a volt-ohm meter. If you don’t own a VOM, buy one and learn how to use it before tackling an appliance repair.

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!! FOR YOUR SAFETY !!

Always unplug an appliance before working on it, or turn off power to it at the main service panel.

If an appliance shocks you, unplug it immediately. Don’t use the appliance until the problem has been corrected.

The capacitors found on certain appliance motors store electricity even after the power is turned off. Always discharge a capacitor before handling it.

Use the proper tools and materials when making repairs—substitutes can create a shock or a fire hazard. Work in a well-lit, clutter-free area. Wear safety gear as necessary, and use insulated tools.

Enlist help to move a heavy appliance.

Beware of sharp edges when disassembling an appliance.

Avoid repairs and electrical work when you are tired, distracted, or in a hurry.

Double-check any repairs you make by testing the appliance for ground faults before you plug it in again.

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APPLIANCE DOES NOT WORK

Power off at outlet?

1. Test receptacle with a lamp you know works. If lamp doesn’t light, receptacle may be faulty (see Replacing a receptacle); more likely, appliance has tripped a breaker or blown a fuse.

2. Check service panel for tripped breaker or blown fuse; reset or replace as needed. It breaker keeps tripping or fuses keep blowing, see Appliance trips breaker below.

Faulty power cord?

A defective cord or plug— often the result of pulling on the cord rather than on the plug—can cause an appliance to fail and can create a shock hazard. With the device unplugged, check the cord arid plug for damage; try to locate and eliminate the cause of cord wear. To replace a plug, see earlier instruction. To test and replace a cord, see below.

Ground prong missing. Appliance will work, but is not safe because grounding circuit isn’t complete. Replace plug.

Bent prongs make it hard to insert plug. They can usually be straightened with pliers, but if prongs are loose, replace plug.

Damaged housing creates a serious shock hazard. Check housing for cracks, chips, or missing insulator. Replace defective plug.

Discolored or pitted prongs indicate overheating or a short circuit. Correct the problem before replacing plug.

Loose wire may have pulled from terminal. Cut Loose wire may have plug off, strip cord to new wire, and reinstall plug.

Frayed cord can expose conductors, usually near plug. Cut off damaged section of cord; reinstall plug.

Worn insulation may expose conductors any where along the cord. Replace cord.

Cord insulation may pull wires. Remove damaged away from plug, exposing wires. Remove damaged cord section; replace plug.

Nicked or cut insulation can be seen by bending cord. Replace cord before conductors are exposed.

APPLIANCE DOES NOT WORK

Servicing 120-volt power cords

1. To test cord for continuity, unplug appliance and disassemble it just enough to access cord terminals. Free cord leads by removing wire connectors, by removing leads from screw or plate terminals (see Making connections), or by desoldering. You may also have to remove a strain-relief fit ting.

2. Set VOM on RX1 scale. Clip meter probes to plug prongs; clip jumper wire across cord leads. Bend and pull on entire cord. A steady zero-ohms reading means cord is OK. A high or fluctuating reading means cord is faulty and should be replaced with a duplicate. Connect new cord leads to appliance leads (using wire connectors) or to appliance terminals.

To check heater cord (removable type) tor continuity, unplug appliance. Set VOM on RX1 scale. Insert VOM probes into female plug; clip jumper wire across male plug. Bend and pull cord along its entire length. If meter reads zero ohms, cord is good. A high or fluctuating reading indicates an open circuit; replace cord and/or plug.

Servicing 240-volt power cords

The power cord in 240- volt appliances usually connects to a terminal block at rear of unit. To access terminal block, unplug appliance, then unscrew and remove terminal block cover plate. Check terminals for discoloration, corrosion, and charring. If there are any signs of damage, replace the block. If the block is OK, test the power cord.

To test a 240-volt cord for continuity, clip jumper wire across outer cord terminals. Set VOM on RX1 scale; clip meter probes to plug’s outer prongs. Bend and pull cord. Repeat test with jumper clipped across middle and one outer terminal; clip VOM to corresponding prongs. Look for steady zero- ohms readings. If readings fluctuate, cord is bad.

To replace a 240-volt cord, remove its strain relief fitting (unscrew a metal clamp-type fitting; use pliers to slightly compress and pull out a plastic fitting that is molded to the cord). Loosen screws that hold cord leads in place, or push out spade lugs from plate terminals. Remove cord; replace with one having same rating and plug type.

Faulty switch?

Appliance switches vary in complexity and functions. A simple on-off switch is easy to test with a VOM, but more complex switches, like a blender’s multiple- position switch, can be trickier to test. A visual check, however, is often enough to detect a fault. Unplug the appliance and disassemble it just enough to access the switch components. Look for and repair any loose or broken wire connections. Clean dirty or pitted contacts. When the switch is closed, the contacts should make a firm connection.

To test on-off switch, unplug device, access switch, and disconnect one lead from switch. Set VOM on RX1 scale. Clip probes to switch terminals or leads; turn switch on. Zero ohms means switch is OK. High or fluctuating ohms means switch is broken or dirty.

Clean switch contacts with an automotive-point file. Flush away any residue with electrical contact cleaner. Contacts should make firm contact when switch is on. If they don’t, it’s usually best to replace switch rather than attempting repair.

Use electrical contact cleaner to clean less accessible switch contacts. In order to work cleaner into switch, operate control buttons as you spray cleaner into apertures.

APPLIANCE DOES NOT WORK

Faulty universal motor?

The power cord, brushes, commutator, and field coil (stator windings) are the likeliest sources of electrical problems in a universal motor. You can test the field coil and commutator with a volt-ohm meter, but a visual check can also provide many repair clues.

(For more on sensory detection of mechanical problems, such as worn bearings and misaligned parts, see Tips from the pros.) Before working on a motor, unplug the appliance. Replace a defective part with a new one from the manufacturer. In the case of an open-circuited field coil or commutator, replace the entire motor or the appliance itself.

Lubricate moving parts following manufacturer’s directions. A drop or two of SAE 10- or 20 weight non-detergent motor oil on end of motor shaft will lubricate bearings. Fill oil cups if motor has them.

Bar-to-bar commutator check. Set VOM on RX1. Touch probes to adjacent bars all around commutator. All readings should be similar. An unusually high ohms reading signals an open circuit; zero indicates a short.

Field coil check. Set VOM on RX1 scale. Clip probes to field coil leads. High ohms or infinity indicates open circuit, The motor in multispeed appliances will have several field coil leads.

Remove brushes from housing and look for damage or wear. In general. replace brushes when they’re shorter than they’re wide. Always replace both brushes.

Brush should move freely in housing; spring should press brush firmly against your finger. Replace weak springs; clean housing and brush with contact cleaner.

Fitting brushes. If new brushes aren’t pre curved, place 600-grit sandpaper between brush and commutator; apply pressure to brush while turning commutator.

Commutator bars are divided by mica insulation. If insulation sticks out, use a small file to flatten it: then use hacksaw blade to grind it below level of bar surface.

Pitting, discoloration, or rough spots on commutator bars indicate short or open circuit in rotor windings. Wear caused by brush contact is OK, as long as bars aren’t pitted.

To polish a rough commutator, hold fine sandpaper around it and turn it. Then burnish bars with hardwood stick. Replace brushes too (they’re a cause of roughness).

Faulty split-phase motor?

Most split-phase motor problems are similar to those in universal motors: worn bearings, a faulty power cord, open-circuited windings. Starting circuitry, how ever, can create special problems. If the motor hums but won’t turn, suspect an open-circuited capacitor or a faulty centrifugal switch. A capacitor that’s shorted can cause a motor to start weakly. If the motor stops after long use or won’t start after stalling, suspect a tripped overload protector.

Discharging the capacitor is a critical safety measure before working on a motor. To make a discharging tool, clip a jumper to each lead of a 20,000-ohm, 2-watt wire- wound resistor (sold at electronics stores). Clip free end of one Jumper to blade of an insulated screwdriver. To discharge capacitor, unplug device, Clip free end of second jumper to one capacitor terminal; touch screwdriver blade to other terminal. If there are three terminals, discharge across outer terminals as well as across center and each outer terminal in turn.

Check discharged capacitor for bulges or leaks; replace if found. Test with VOM on RX100 scale. Clip probes to terminals. Reading should jump toward zero ohms, then drift to high. Reverse probes and test again; look for same reading. Steady zero ohms indicates a short: steady high ohms, an open circuit. If capacitor has three terminals, test with one probe touching center terminal and second probe touching each outer terminal in turn.

Centrifugal switch can stick in open position (motor won’t turn) or closed position (motor shuts down soon after starting). Look for dirty contacts or stuck mechanism. Clean contacts with automotive-point file and contact cleaner. Lightly oil pivot points. Replace switch that has burnt terminals.

Manual overload protector has a reset button that lets you start a stalled motor (check first for binding parts). If overload protector is internal, turn off appliance, let motor cool (this may take several hours), then restart appliance.

Faulty shaded-pole motor?

Shaded-pole motors seldom break down in normal use, and when they do, it’s usually best to replace the entire motor or the appliance itself.

To test a shaded-pole motor for continuity, unplug appliance and disassemble. Set VOM on RX1; clip meter probes to both leads from field coil. Reading of infinity means motor is defective and should be replaced.

To service a shaded-pole motor, remove rotor from field. Clean dirt and corrosion with electrical contact cleaner. Lubricate shaft with oil and remove excess.

APPLIANCE TRIPS BREAKER

Circuit overloaded?

When an appliance trips a breaker or blows a fuse, the circuit is probably over loaded. Trace circuit (see Correcting circuit overloads) and reduce the number of appliances on it. If problem persists, suspect a shorted cord or motor.

Short circuit?

To test motor, unplug appliance and disassemble. Set VOM on RX1 scale. Clip VOM probes to each field coil lead. Motor is shorted it meter reads zero ohms. Steady high ohms means motor is OK.

To test cord, unplug appliance and disassemble sufficiently to access cord terminals. Disconnect one cord lead. Set VOM on RX1 scale. Clip VOM to plug prongs. Bend cord. Zero or fluctuating ohms indicates short. Steady high ohms means cord is OK.

APPLIANCE SHOCKS USER

!!! Ground fault?

A frayed power cord or an electrically live component that touches a metal appliance part can deliver a serious shock. If handling a power cord gives you a shock, the cord is defective; replace it without delay. A breakdown of wiring insulation can cause a live conductor to touch the metal frame of an appliance. If the appliance is grounded, the resulting short to ground will trip a circuit breaker or blow a fuse. If the device is not grounded, ground-fault, or leak age, current will charge the frame and shock anyone touching the appliance.

To test for a ground fault, unplug appliance. Set VOM on highest ohms scale (usually RX1 000). Touch one VOM probe to metal frame or part; touch second probe first to one plug prong, then to the other. Meter should show infinite resistance. A lower reading indicates a ground fault.

To locate cause of ground fault, unplug and disassemble device; check internal wires for bare spots. Clip a VOM probe to a metal part; clip other probe to plug. Turn switch to On or High; bend and pull wires. If reading jumps as a wire moves, that wire is grounded; replace it. If you can’t find the fault, have appliance professionally serviced.

Electronic components

Solid-state electronic components are often used to monitor or control the operation of an appliance or power tool. When troubleshooting an appliance with electronic components, first eliminate mechanical or electrical parts as the cause of the trouble. If these parts are OK, you can assume that an electronic component is probably at fault.

Digital readouts. Liquid-crystal displays (LCD’s) or light-emitting diodes (LED’s) are sometimes used to indicate a knob setting or show the time. Check non- working readouts for loose or dirty connections first. Readouts that are easily removed can be replaced if faulty, but it’s often more practical to replace the entire circuit board containing the readout.

Diodes, resistors, and capacitors. A diode allows current to flow in one direction only, while resistors limit the amount of current flowing through a circuit. Capacitors store electrical energy, releasing it on demand to provide a momentary burst of extra current (see For your safety). These components are often found on or near switches and motors.

How to test a diode:

To test a diode for continuity, unplug the appliance; disconnect one end of the diode. Set a VOM on the RX1 scale (or on the diode function, if any; consult your owner’s manual). Probe both ends of the diode; then reverse the probes. If one reading is low and the other infinity, the diode is OK. The same reading in both directions indicates damage. To make sure cur rent flows properly, install a new diode so that its identifying band is on the same end as the original’s.

With VOM on RX1, touch probes to both ends of diode.

Reverse probes. One reading should be low, the other infinity.

How to test a resistor:

Unplug the appliance; disconnect one end of the resistor. Electronic components are usually soldered, in place, so you may have to desolder the connection. Set a VOM on the RX1 scale (or the next highest scale above the resistor’s rating); touch its probes to the resistor’s leads. The meter reading should be within 10 percent of the resistor’s rating. The reading may rise or fall slowly within this range during the test.

Compare meter reading to resistor’s rating.

How to test a capacitor:

!!! A capacitor stores electricity after the device to which it’s connected has been turned off. Even if the capacitor is a small one, such as those found within some electronic devices, you must discharge it before working on the circuit. To discharge a capacitor, see General troubleshooting. To test the capacitor in an electronic device, desolder one end. Set the VOM on the lowest resistance scale; touch its probes to the capacitor’s terminals. The meter should show low resistance, then resistance gradually increasing toward infinity. Reverse the probes; the results should be the same. If the results differ, the capacitor is defective and should be replaced.

Discharge and disconnect capacitor; attach VOM probes to terminals.

Reverse probes. Readings on both tests should start low, then rise slowly to infinity.

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Reading diodes and resistors:

One end of a diode is usually marked with a band indicating the direction of current flow; electricity should enter on the unbanded end. To read a resistor’s color code, the bands closest together must be on your left. The first three bands identify the resistor’s capacity in ohms: The first two represent single digits; the third indicates the number of zeros that 10110w the first two numbers (see below). Band four represents an accuracy tolerance: gold indicates +/-5%; silver, +1-10%; no band, +/-20%. A fifth band is sometimes included to indicate the estimated failure rate of the resistor.

Resistor: The color bands above indicate a capacity of 8,600 ohms and a tolerance of +1/-5%. The lack of a fifth band means that the resistor does not have a failure rating.

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Electronic touch-pad controls:

Touch pads are sealed switch assemblies. If the entire pad does not work, check the circuit board or pad wiring for faulty connections. If a single button does not work, clean its contacts (if accessible) by rubbing them gently with a pencil eraser and then wiping with a foam swab dipped in alcohol. If the pad still does not work, replace the entire assembly.

Electronic touch pads, such as those found on microwave ovens, are layered assemblies that usually cannot be repaired.

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