Electric Furnace Limit Switch Test

A clogged up furnace filter will block air flow into a furnace and raise the temperature inside it.

Electric furnace limit switch test.

How to check limit switches using your voltmeter. If it reads ol you need a new switch or maybe hit the reset button if it has one. Limit switches are easy enough to ohm out in plug the furnace and disconnect one of the two wires from the limit switch. Turn off the electricity to your furnace before you test the primary limit switch and wait about 10 minutes to give it time to cool down.

Fan limit switch moves past fan off then past fan on blower doesn t start until about 10 20 degrees above fan on then blower runs on for 30 seconds and shuts off for a few minutes turns back on for 30 seconds and shuts off for a few minutes. Lack of continuity indicates a defective switch. All the thermostat does is close a switch which starts the entire heating process. You can also test the limit switch with a digital voltmeter.

If the temperature inside the unit becomes to high the high limit switch will turn the gas off to the unit. Example limit switch on amazon honeywell l4064b2236 combination fan and limit furnace control. Things to check first.