How to Test a Dryer Door Switch. Many people may not know this, but dryers have a door switch that makes it impossible for them to operate when the door is open. This safety switch can sometimes go bad, however, and if you do happen to have a dryer that can run with the door open, then there may a problem with your door switch. Likewise, if you have your door closed and the dryer is not operating the way it is supposed to, the door switch could still be the culprit. Here is how to test the door switch on a dryer to determine if that is the cause of the dryer's ailments.
As always, before working on your dryer, be sure to unplug it or turn off the circuit breaker that is supplying the power to it. Additionally, if your dryer uses gas, be sure to turn the gas feed off too.
Next, the door switch is located, you guessed it, on or around the door area. Open your dryer's door and you should see a small white prong sticking out. Inspect the switch and see if it is stuck in the closed position. If it reacts normally, like a spring-loaded button, then you are going to have to access the wiring.
Dryer door switches vary per manufacturer. Some can be popped out using a flat screwdriver, some have a set-screw holding it in place and others can only be accessed by opening up the dryer cabinet. Determine which kind you have.
Since popping out the switch or unscrewing it are self-explanatory, we will discuss how to get inside the dryer cabinet. First, you will have to determine your area of entry, which varies by manufacturer. Some dryers may have a lower front panel that can be unscrewed and removed or lifted up and off. Other dryers may offer access only from the rear of the machine. This will require the removal of quite a few screws. The last type of dryer entry would be from the front, where the drum is located. This panel actually supports the drum, so removing it is tricky and can prove to be difficult to work with and reinstall.
In each of these cases, once you find the door switch, there will normally be two plastic compression wings securing to the machine. Use a flat screwdriver or putty knife to press one of the wings in so it can be popped out of the hole.
Now that the switch is exposed, inspect it for any arcs or scorch marks. Check the wires and the connectors to ensure that they are in good shape. If everything looks good, you can now test the switch.
Before testing the switch, remove the wires by using the needlenose pliers to pull them off the terminals. Be sure to avoid pulling on the actual wires themselves; only pull on the connector! Pulling on the wires can cause them to break or pull out of the connector. Make sure you know which wire goes to which terminal so you don't have a problem when you put everything back together.
With the switch free of its connections, set your multitester to read continuity. This is the setting on the tester that reads ohms and it is usually marked either RX1 or X1. If your multitester came with alligator clip accessories, it would help if you put them on the tester leads. If not, don't worry, you can still test the switch.
If you have the clips, clip one lead to each terminal on the switch. If you don't have the clips, just touch one probe to one terminal and the other probe to the other terminal. The tester should display a reading of infinity.
Keeping the probes touching the terminals, push in the switch (this is where having the clips comes in handy!). With the switch pushed in, your tester should display a reading of zero. Release the switch and it should return to infinity. If you do not get these readings or the tester reads infinity or zero at all times, then you will have to replace the door switch.