Hi JS, Very good advice in your post. However, you say "NOTE: If the thermal...
This advice is general in nature, but should assist you in isolating MOST dryer malfunctions.
Normally when a dryer starts to exhibit longer dry times, then suddenly stop working, it is an indication that the Thermal Cut-Out (TCO) or Heating Element has blown. But…what causes this to happen?
First, a little dryer theory: A dryer needs air to breath. Proper ventilation is required for the heating circuits to regulate the internal air temperature properly. If you have to keep placing items back in the dryer to dry again, or the dryer just doesn’t seem to be putting out hot enough air, it may be time to think about checking the dryer vent ducting (a simple separation of more dense clothing from lighter weight clothing can help shorten dry times too). If the heating circuits are starved for air they actually OVERHEAT and can cause problems. This is why the outside case can feel hot, but the drum inside feels cold. The TCO acts as a fuse for the heating element circuits. When an overheat condition occurs, the hi-limit thermostat is supposed to open to shut off the heating element. This is how the dryer regulates its heat. However, if the hi-limit thermostat malfunctions, the TCO will blow. This device acts as a fuse, is not resettable, and has to be replaced. This also means that the hi-limit thermostat could be suspect and it should also be replaced at the same time. Most manufacturers recommend replacing the two components together and are sold as a set.
Now...if your dryer has been having problems drying, the first thing you need to check is the ventilation ducting to ensure that it is not kinked or clogged. Poor air flow is the number one cause of dryer failures. Not to mention it can cause fires due to lint backing up inside the dryer. This could be the "electrical" smell a lot of people complain about. If lint accumulates on the heating element it will smolder and burn. It is often reported that you should clean your ducting twice per year. I recommend the ducting be checked (this means inspected to see if it needs cleaning) thoroughly about once per season. That's 4 times per year. If you've never cleaned the ducting, or your dryer is pushed all the way up against the wall causing the ducting to become kinked, you will have air flow problems. One way in determining air flow is to remove the vent hose from the back of the dryer and start the dryer (of course, you need a working dryer in order to do this). The air should be forceful and slowly warm up to about 140 degrees. If the air flow is weak, you may have a clog inside the air baffle of the dryer (this is where the lint screen slides into). If the air flow is good, reattach the dryer hose and check at the output of the dryer vent as it exits your home. If the air flow is weak or non-existent then you know you have a clog in the vent line somewhere. Periodic cleaning will go a long way towards preventing future clogs. Dryer vent rule of thumb: The SHORTER and STRAIGHTER the vent line, the BETTER. Everywhere you have a bend or kink is an area where you will create potential collection points for lint. Poor dryer maintenance is also one of the frequent causes of house fires.
How to troubleshoot a dryer: If your dryer has the lint screen on top of the unit, you will need to remove the back panel to get to the heating circuits. If your dryer has the lint screen in the door, you will need to remove the lower kick panel under the door by pushing in on the release tabs with a putty knife. They are located along the front seam about two inches in from each side. CAUTION: It is recommended that you unplug the dryer BEFORE servicing the inside or cleaning. There are still dangerous voltages present even with the machine turned off.
Symptom:
Dryer Runs, But Does Not Heat:
Suspected Components:
1. Heating Element (located inside the heater box) - Resistance reading should be 9-13 ohms.
2. Thermal Cut-Out (located on the heater box) - Resistance reading of 0 ohms.
3. Hi limit Thermostat (located on the heater box closest to the heating element leads) – Resistance reading of 0 ohms.
4. Operating Thermostat (located on the air baffle) - (May have 4 wires attached to it). Will read 0 ohms across one set of leads, approx. 7 ohms across the other.
5. Bad Heater Relay (usually located in the console) – this is not equipped on all model dryers. However, on dryers that DO have them, this acts as a switch and turns the heater circuits on at the push of the START switch.
Dryer Does Not Run At All:
Suspected Components:
1. Thermal Fuse (located on the air baffle) - Resistance reading of 0 ohms. NOTE: If the thermal fuse is blown, the drum light will not come on.
2. Broken Drum Belt - If dryer is equipped with a broken belt relay, this will shut the dryer down.
3. Broken Door Switch - If the door switch is broken, this will shut down the entire dryer as no power is applied to the start switch with the door switch open.
4. Bad Start Switch - If the start switch does not toggle close or stay closed when released, the dryer will not start.
5. Bad Timer - If the timer does not function the dryer will not start.
6. Bad Drive Motor - No Motor, drum does not rotate, heating circuits may or may not function. DOUBLE CHECK the CONNECTOR PLUG on the Drive Motor. I have found situations where this plug came loose for whatever reason and caused the dryer to either shut off completely or work intermittently.
7. Bad A/C Receptacle and/or Connector Plug - If you aren't getting the proper voltage to the dryer, it will not run.
These recommendations for TROUBLESHOOTING are not all inclusive as different manufacturer models vary in components and configuration. However, the general cleaning maintenance and proper ventilation requirements should apply to ALL dryers.
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