Ultimate Fix-It-Yourself Manual: Large appliances--Dryers

A clothes dryer circulates heated air through wet clothing in order to evaporate the moisture. Its main components are a drum to hold and tumble the clothing, a heat source, a blower to circulate the hot air, an electric motor to turn the drum and the fan, and operating controls. The heat source in an electric dryer consists of heating coils. A gas dryer contains a burner.

Poor drying is often caused by lint buildup in the screen or in the exhaust system, although heater parts, the fan, or faulty seals around the drum or dryer door also may be to blame. Another common problem is a broken drum belt, which prevents the drum from turning.

Components:

• Thermal cutoff
• Heater (inlet) duct
• Heating coils
• High-limit thermostat
• Drum belt
• Drum roller
• Blower
• Lint screen
• Lint (exhaust) chute
• Drum seal
• Bulkhead
• Door spring
• Centrifugal switch

Note: Details of repair and disassembly may vary, depending on appliance model. If year dryer differs markedly from this model or the common variant.

= = = FOR YOUR SAFETY = = =

Turn off power to a dryer before fixing it. Unplug a gas dryer; trip breakers or remove fuses that control an electric one (most electric dryers are wired to a 240-volt circuit controlled by double circuit breakers or two cartridge fuses in the service panel). An electric dryer cabinet should be grounded to the neutral line at the terminal block or to a metal cold-water pipe. A gas dryer is grounded through the power cord’s grounding conductor.

Internal dryer wiring is heat-resistant. Never substitute ordinary wiring.

Shut off the gas supply to a gas dryer by turning valve to Off position (handle perpendicular to supply tube). If you disconnect gas line, test for leaks after you reconnect: Mix equal parts of cold water and dishwashing liquid and apply to joint; tighten fitting if bubbles appear.

If you smell gas, open windows. Put out any flames. Don’t touch electrical switches or use the phone. Evacuate the house. Call the gas company from a neighbor’s house.

Troubleshooting:

[Degree of difficulty: Simple, Average, Complex • Volt-ohm meter required:I]

Gaining access:

To open control panel, take out screws at ends; tilt panel forward and remove rear plate.

CAUTION: Unplug dryer or turn off power to it before fixing it.

To lift top, remove lint screen and any top screws. Wrap putty knife with masking tape; insert it under top about 2 in. from each corner to release clips.

To remove rear panel, take off exhaust vent and loosen screws around edges with a nut driver. On a gas dryer, be sure to shut off gas supply first.

Free toe-plate by pressing with stiff putty knife against spring clips located above ends of panel. On some models, take out screws at ends instead.

To remove front panel, take off toeplate and take out screws just under front edge of panel on either side. Unhook and remove door springs.

Next, lift top. Disconnect and unhook door switch wires, loosen inside screws, and lift off panel. Put wood blocks under drum to support it.

Control panel:

A dryer’s control panel usually contains the push-to-start switch, the tempera ture selector switch, and the timer. On most dryers, the temperature selector controls one or more thermostats that regulate the temperature, but on some, this switch is an adjustable thermostat with a capillary sensing tube and is tested like the one on an electric range. Test a temperature switch with two selections as shown below. To test one with more options or to test a timer more fully, see ---.

Some machines have other control- panel switches that govern an extra- care cycle or an end-of-cycle signal; test them like a simple on-off switch or a selector switch.

Testing the switches and timer:

Test start switch with VOM on RX1. Remove one lead from switch; clip probes to both terminals. Look for infinity reading. Then press Start button; reading should change to zero.

Test temperature selector switch with VOM set on RX1. Remove leads and touch probes to terminals. Turn switch. Reading should change from zero to infinity or vice versa.

To test timer motor, disconnect both leads. Set VOM on RX100; clip probes on leads. Look for moderate resistance; if reading is very high or infinity, replace timer motor.

Door problems:

Dryer doors have a seal to keep hot air in and room air out. To check the seal, hold a piece of tissue near the edge of the door while the dryer is running. If the tissue is drawn in, examine the seal for looseness and replace it if it’s worn, damaged, or has hardened. Install an identical new door seal. Dip it in warm soapy water to make it pliable; let it dry well. Use the special heat-resistant RTV silicone adhesive that comes with the seal (or is available from the same sup plier). Avoid twisting the seal or pressing too hard. If the dryer door is loose, replace the catch, strike, or both.

All dryers have a door switch that cuts off the motor when the door is opened, preventing the drum from turning unless the door is closed. The door switch on most dryers is reached by lifting the top panel. On some models, it’s attached to one of the door’s hinges.

To replace door seal, pull or pry off old seal and remove old adhesive with mineral spirits. Press on new seal with putty knife, using special heat-resistant RTV silicone adhesive sold with seal.

To replace door catch (left), take off front of door. Then use needle-nose pliers to squeeze catch and any tabs on it; push catch out. To remove strike (right), squeeze it and pull out.

Testing and replacing the door switch:

1. Disconnect leads. With VOM on RX1, probe terminals. Look for reading of zero with door closed, infinity when open. If switch is wired to a light, look for reverse readings on light terminals.

2. To replace a defective switch, remove screws £ from front, then lift switch out from inside dryer. On some models, you must pry switch free with screwdriver, as on a refrigerator.

Drum and drum belt:

Most drums are supported on rollers and turned by a belt that wraps around the drum. A steady rumbling or squealing often means worn rollers or a bad idler pulley bearing; a thumping sound, a worn belt. If the belt or idler pulley is broken, the motor will run but the drum won’t turn. A screeching sound can signal an object stuck in the drum seal. To clear the seal, insert a putty knife in the edge and turn the drum one full turn. The seal should fully cover the ridge on the rear panel.

To remove worn drum belt, push idler pulley toward motor to loosen belt tension. Then pull belt off motor pulley. Slide belt off drum.

Install new belt around drum over mark left by old belt. At bottom, form loop with belt and route it under idler pulley and over motor pulley.

To remove a defective idler pulley, unhook bracket from dryer floor (or remove spring and mounting screw or clip). Replace entire pulley unit.

Install new drum seal with stitched side up and center fold against drum edge. Lift edge of seal and apply heat-resistant RTV silicone adhesive.

To replace worn roller, remove drum. Unscrew roller support bracket if necessary, and pry retaining clip from shaft to free roller.

Motor and blower:

Dryer motors are split-phase and operate on 120-volt current. Except for testing and replacing the centrifugal switch, most newer motors are not repairable and must be replaced if they test faulty.

The centrifugal switch governs the motor’s start and run windings and allows power to reach the heater or burner only after the motor is up to speed. Testing ft may require the aid of a wiring diagram to determine which leads come from the motor.

To test centrifugal switch, take off leads and set VOM on RX1. With button out, probe both heater terminals (often marked Hi and H2 or coded red); then probe push-to-start and neutral terminals. Look for zero reading on both tests. Next, probe push-to-start and start terminals; look for infinity. With button in, all readings should be reversed.

To remove blower, grip blower hub (which has left-hand threads) with a wrench; then use a second wrench to turn motor shaft clockwise.

At back, unscrew lint chute and push it aside. Remove blower from motor shaft. Check blower for cracks and damaged threads and fins.

To remove motor, disconnect its leads from switch and remove blower. Release motor by disengaging spring clamps (some clamps unscrew).

Test motor with VOM on RX1. Take motor leads off centrifugal switch. Probe common lead (here, blue) and other leads in turn; look for low ohms.

Electric heater and thermostats:

If a dryer doesn’t heat, look for a tripped circuit breaker or blown fuse , then test the dryer’s thermostats, thermal fuse, thermal cutoff, and heating coils. Make sure the coil terminals are clean and tight. Also check the coils for a ground fault: With the VOM on RX100, probe the heater duct and each terminal in turn; look for an infinity reading.

If a thermostat has a second set of terminals, they go to an internal heater that activates the thermostat early when the heat setting is Low. If a dryer gets too hot on Low, test these terminals with a VOM on RX1; look for continuity with moderate resistance.

Opening a dryer’s back panel gives you access to the heater duct that contains the heating coils. It also lets you reach the operating thermostat and thermal fuse on the blower housing and the high-limit thermostat and thermal cutoff on the heater duct. Some dryers have three operating thermostats; all are tested as shown at right. Still other dryers have a capillary thermostat with a sensing tube and an adjustable control; test it as you would the similar device on an electric range. High-limit thermostat; Heating coil terminals

= = = USE AND CARE = = =

Clean the lint screen after each load.

Remove the lint with your fingers; don’t rinse or wash the screen. When reinstalling the screen, make sure it’s seated fully. Vacuum lint from the heater area, lint chute, blower housing, and exhaust duct connection at least once a year, and any time you service the dryer. Avoid damaging the wires.

Clear the outdoor vent hood with a soft wire. Avoid vent duct sags and turns of 90-degr. or more; they can trap water and lint. It’s safest to use 4-inch-diameter rigid metal duct whenever possible. Limit flexible ducts to short runs.

Correct--Incorrect

= = = =

Testing thermostats, thermal fuse, and thermal cutoff

To test a thermostat, set VOM on RX1, remove a lead, and probe terminals (outer two terminals if there are more than two). Look for a reading of zero.

Remove thermostat; put it in an electric skillet heated to temperature higher than that stamped on device’s metal flange. Test again. Look for infinity reading.

To test thermal fuse (or thermal cutoff), set VOM on RX1, take off a lead, and probe both terminals. Look for zero reading; replace if high or infinity.

Testing and replacing heating coils:

1. Test heater for open circuit. Remove leads, set VOM on RX1, and probe terminals. Look for reading of 5 to 25 ohms. If reading is zero, replace coils.

2. Disconnect thermal cutoff and thermostat from duct. Then open top and remove screw holding duct. Lift duct off brackets and pull out back.

3 Remove screws holding coils in duct; gently slide coils free. If coils are stretched and bent, look for obstruction blocking airflow.

Gas burners:

Gas dryers generally suffer fewer problems than electric models. Have a faulty burner or ignition professionally serviced. If the burner has an air shutter, however, you can adjust it to admit more or less air. A yellow burner flame indicates too little air. A roaring sound (or popping when the burner shuts off) signals too much air—a common problem in dryers using bottled gas, but it can occur with natural gas as well.

Adjust air shutter by loosening thumbscrew and rotating shutter until burner flame appears light blue but does not roar. Retighten screw.

Common variant: Front blower and circular heating coils

In the popular dryer model featured above, the blower inlet is in front under the drum and is visible when you open the door. Its heating coils are attached to the rear panel in a circular pattern (or enclosed in a cylinder under the drum). The drum is supported by a rear bearing shaft.

Most tests and repairs require removing the drum. If the drum won’t lift out easily after you open

the cabinet and release the drive belt, you may need to remove slides that hold the drum to the front bulkhead. Also, the drum’s rear shaft may be held by a retaining ring, reached through a small access panel on the back.

Always replace both heating coils even if only one is faulty. To heat properly, new coils must be stretched uniformly and be the same length as the originals. Don’t overstretch a coil.

Gaining access:

1. Open top by removing the screws under the front edge that secure the top to the front panel. Then lift the top and tilt it to the rear. 2. To remove front panel, disconnect and unhook wires to door switch and light. Then take out screws that join panel to cabinet.

3. Pull panel forward to disengage door frame and lint chute on panel from drum. Then lift it up to free it from legs and hook-on connections.

4. A To release drum belt, reach though lower back opening. Push idler pulley toward motor to relax belt tension while you slip belt off motor pulley. 5. Remove any bolt or retaining clip on drum’s rear shaft through rear access panel. Then lift drum, slide it out, and slip the belt off. 6. To remove motor, pry off bracket over its back end, unscrew blower blades in front, and then unscrew clamp connecting motor to blower.

Testing and replacing circular heating coils:

1. Remove coil leads. With VOM on RX1, probe common terminal and other two terminals in turn. Look for low ohms reading. Also test for ground. 2. To replace coils, use pliers L to flatten small tabs on terminals; then pull terminals through terminal block. (Some coils are bolted to terminals.)

3. If new coils need stretching, use old coil or cord threaded along path as guide. Wearing safety goggles, grip coil in vise and pull evenly with pliers.

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