Testing a door switch
| Note: | | Disconnect the power source to your dishwasher before you conduct this or any other test. Either unplug the unit from the wall outlet, remove the appropriate fuse from the fuse box, or flick the appropriate breaker in the circuit breaker panel. |
Before you test the door switch, examine the prong attached to the inside of your dishwasher tub. This prong comes in contact with and activates the door switch when the door is closed. Perhaps the prong on the inside of your dishwasher is missing or damaged, leaving it incapable of activating the door switch.
A door switch is a simple on/off mechanism that prohibits the dishwasher from operating when the door is open. Dishwasher door switches are only an inch long. Most are black in color and all have metal prongs, called terminals, extending out from the body of the switch.
Some door switches have only two metal prongs extending from the body, while others have three. Those with three terminals will have a common (COM) terminal, a normally closed (N.C.) terminal, and a normally open (N.O.) terminal. Those switches with only two terminals will have either a common terminal and a normally open terminal, or a common terminal and a normally closed terminal. We are providing directions for testing a door switch with three terminals. If you are dealing with a door switch that has only two terminals, ignore the part of this test that does not apply to you.
Locate your dishwasher's door switch. The control panel in the front of the unit may be easily removeable, allowing you access to the switch. In some cases, you will have to first remove the inner panel of the dishwasher door. This is usually accomplished with the removal of a few screws. Be careful to not remove the screws at the bottom of the door that are actually a part of the hinge assembly. Removing these screws will remove the door from the unit, which is unnecessary for this test. With the inner door panel removed, you may or may not discover an even smaller panel covering the back of the control panel at the top of the dishwasher door. This smaller panel is held in place with either a couple of screws, or a couple of clips. The switch you are looking for will be located behind this much smaller panel and it is commonly integrated with the door latch assembly.
Using caution, remove all wiring harness leads from the switch's terminals. You may need to use needle nose pliers to pull gently not on the wire itself, but on the metallic wire connector. Be aware that some door switches may have a locking clip keeping the harness from coming loose. In this case, there is a protruding lever which must be depressed while the harness is gently pulled away from the terminal.
Use your ohmmeter to test your switch for continuity. Begin by setting your ohmmeter to measure resistance at a scale of Rx1. Touch the metal tips of the test leads together and zero your ohmmeter by adjusting the thumbwheel in the front of the meter until the needle reads '0' on the scale.
Touch one meter lead to the COM terminal and the other lead to the N.O. terminal. Do not push in on the actuator. Your meter should give a reading of infinity, meaning the circuit is open, and there is no continuity. Without moving the meter's leads, press down on the actuator until you hear a 'click'. With the 'click' of the actuator, the meter should produce a resistance reading of zero ohms. This means the circuit is closed and continuity is present.
| Hint: | | The presence of a distinct 'clicking' noise is evidence that your switch is working as it should. Be that as it may, switches with only two terminals do not 'click' when actuated. |
Keep the meter lead that is touching the COM terminal in place, but move the other meter lead from the N.O. terminal to the N.C. terminal. You should receive a reading of infinity when you push in on the switch's actuator. When the actuator is released, you should receive a resistance reading of zero ohms.
Now, set your ohmmeter to its highest resistance scale and touch one meter lead to the N.O. terminal and the other meter lead to the N.C. terminal. The resistance reading between these two leads should be infinite.
Finally, take a resistance reading from both the N.C. terminal and the N.O. terminal to any metal mounting hardware that is a part of the switch assembly. You should receive a normal reading of infinity.
Any readings that differ from the ones presented here are indicative of a defective door switch that will need to be replaced.
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