Testing Furnace Pressure Switch

To do this the pressure switch wires are removed and the furnace turned on.

Testing furnace pressure switch.

The draft inducer should start. To test the pressure switch use a multi meter and measure the continuity of the switch as it opens and closes. The switch wires have to be removed first. The switch is being tested to check if it s closing when the diaphragm is pulled in.

There should be either two or three wires going into your pressure switch. Turn off the power to the furnace by switching off the disconnect switch located near the furnace. The pressure switch has a pressure at which it closes which is typically negative. Probe one lead of the pressure with one lead of your meter while touching the other lead of your meter to.

With a manometer or magnahelic. How do you test the gas furnace pressure switch. Basically the switch needs to be tested to see if it is closing when the pressure diaphragm pulls in. The steps are as follows.

A multimeter will be needed to test the switch for continuity. Turn off the power. If you see anything clean it out. If there is no disconnect.

Check for obstructions in the hose. Set your meter to volts ac turn your furnace on so it is calling for heat. Ensure the draft is above the required pressure.