When fixing a broken appliance, it’s sometimes not always obvious if the part is faulty. Sometimes a visual inspection will tell you if a part needs replacing, like a corroded bake element, or a broken dryer belt. However, for some parts like a switch, fuse or electrical component, you will need to test the part using a test meter (also called a multimeter or a volt-ohm meter) in order to check it for continuity.
Continuity is an electrical term that means that electricity can pass through the component without restricted flow or resistance. Resistance is another electrical term that measures the opposition to electric current flow while it passes through a conductor – like an appliance part.
Some appliance parts will have zero continuity, meaning that electricity can pass through the component without resistance and that the part is good and working. Other parts will have some resistance, but this is considered normal and the part will still be in good working order. Again, it depends on the part being tested. Some parts have varying levels of resistance depending on the temperature the part is exposed to at the time of testing, like a refrigerator bimetal thermostat or a dryer ignitor.
To know the correct level of resistance for the part you are testing, consult the technical information sheet for that part or a manufacturer’s troubleshooting manual.
Before testing any part:
- always disconnect the power supply before removing parts or disassembling an appliance
- always disconnect the wiring connected to any electrical component you’re testing
- always hold the multimeter leads or probes by their insulated terminals when testing a part
Getting Ready to Test
You can use either a digital or analog meter in order to test your part. If you use an analog meter (which gives readings in a scale or gauge), you will need to make sure it is properly calibrated before testing your part.
- Set the multimeter to Ohms and to the lowest setting on the scale (Rx1 or 200 ohms).
- Plug the test lead probes into the meter with the red lead going to positive or the Ohm symbol (Ω) or letter “R,” and the black going to common or negative.
- Touch the two lead ends together. Make sure that the scale needle points to “0” and adjust the
Ohm Adjustment Knob (Ω) to get the needle as close to zero as you can.
You do not need to calibrate a digital multimeter, but you do need to set it to the correct scale. Digital meters are usually considered more accurate and can sometimes measure temperature as well.
You are now ready to test your part.
Testing your part
To test your part, touch one end of the lead to one terminal, or contact point of the part, and the other to the opposite terminal or contact point of the part. If you get a reading of zero, then the part is good or has continuity.
Generally, you need to know how much resistance you are supposed to be getting from a given part. Switches, fuses, water valve solenoids all have relatively low resistance and the scale can be set to the lowest setting of Ohms of resistance.