Testing Furnace Pressure Switch

Check for obstructions in the hose.

Testing furnace pressure switch.

How do you test the gas furnace pressure switch. The switch is being tested to check if it s closing when the diaphragm is pulled in. Basically the switch needs to be tested to see if it is closing when the pressure diaphragm pulls in. Turn off the power.

If there is no disconnect. Inspect the pressure switch hose. A multimeter will be needed to test the switch for continuity. Hook a manometer to the tubing and check the draft from the heat exchanger in inches w c.

To do this the pressure switch wires are removed and the furnace turned on. If you see anything clean it out. The steps are as follows. Set your meter to volts ac turn your furnace on so it is calling for heat.

The pressure switch has a pressure at which it closes which is typically negative. To test the pressure switch use a multi meter and measure the continuity of the switch as it opens and closes. Turn off the power to the furnace by switching off the disconnect switch located near the furnace. Probe one lead of the pressure with one lead of your meter while touching the other lead of your meter to.

Ensure the draft is above the required pressure. With a manometer or magnahelic. The switch wires have to be removed first.