How to Test an Electronic Switch

Test your electronic switch using an ohmmeter.

Typically, the simple fix to a light that won't turn on is replacing the bulb. Another potential problem with a malfunctioning light, however, is a malfunctioning switch. A problematic switch can send out sparks or stop working altogether. There is a test to see if your switch is the problem or if it is something deeper, such as your light fixture or wiring. Take all possible safety precautions when working with electricity and if you are inexperienced with electronic switches, consult a professional.

Things You'll Need

• Black wire lead with alligator clip
• Red wire lead with alligator clip
• Masking tape
• Marker
• Electrical tester
• Long-nose pliers
• Ohmmeter
• Screwdriver

Instructions

1. Flip the switch to the "off" position. Turn off the power to the light switch using your circuit breaker. Take off the cover plate and unscrew the screws that connect the switch to the electrical box.

2. Use your electrical tester to make sure that the switch isn't still charged with electricity. If the tester detects electricity, wait a few hours and test the switch again. If you detect no electricity, carefully remove the switch and unwrap the wires of the switch with the pliers. Clearly mark which wire goes to which terminal of the switch.

3. Turn on your ohmmeter and make sure that it is set in the ohmmeter mode. Change the resistance range to "x1" unless your device has an autorange function.

4. Connect the wire leads into the meter and tap the probes together to ensure that the ohmmeter is working properly. When these probes touch, the meter should read less than one ohm.

5. Attach the red lead probe to one terminal of the switch. The terminal is a set of screws located on the side of the switch. Attach the black lead probe to the other terminal. Flip the switch to the "on" position. The meter should read one ohm or less.

6. Flip the switch to the "off" position. The meter should read "OL" or have a higher resistance than one. Flip the switch back and forth between "on" and "off" and observe the display of the ohm meter. The reading should change from one ohm or less to the "OL" or high resistance. If it does not, this means that the switch is broken. Replace the defective switch.

References

• T Equipment Net: M-1700 Operating Instructions
• Home Tips: How to Check a Standard Light Switch
• Appliance Aid: Electrical Testing Tips