[rmac18]

Furnace ignitor doesn't light. Error Code on the PCB says Pressure Switch is open. How do I fix this?

[KC13]

Try tapping on the pressure switch while the furnace is attempting to run. Check pressure switch hose(s) for breaks or blockage. Check flue/intake/exhaust vents for blockage. If condensing furnace, check drain trap/tubes for blockage.

[rmac18]

Thanks for your response KC13. I tried tapping on pressure switch while attempting to run. Checked pressure switch hose and it seems to be unblocked and in fine condition. There is another PVC pipe above the heating unit that connects to a drain, It's not easily accessible but it doesn't appear to be blocked, the drain works fine and there is no trace of water anywhere. Still get exactly the same symptoms, the unit blower kicks on and then after a few minutes it kicks off and I see the error code on the PCB that says Pressure Switch is open. The Ignitor never lights and it never seems to get past the initial step of the startup sequence. Any other ideas.

[rmac18]

Thanks for your response KC13. Sorry for the double post I just realized that I put my response in the wrong box. I tried tapping on pressure switch while attempting to run. Checked pressure switch hose and it seems to be unblocked and in fine condition. There is another PVC pipe above the heating unit that connects to a drain, It's not easily accessible but it doesn't appear to be blocked, the drain works fine and there is no trace of water anywhere. Still get exactly the same symptoms, the unit blower kicks on and then after a few minutes it kicks off and I see the error code on the PCB that says Pressure Switch is open. The Ignitor never lights and it never seems to get past the initial step of the startup sequence. Any other ideas?

[KC13]

Try this: straighten a paper clip, remove the pressure switch hose from the vacuum port on the furnace, and check port for blockage.

[rmac18]

Thanks again KC13, I removed the pressure switch hose entirely and checked the vacuum port for blockage. I didn't feel anything and the paper clip was about 4 inches long. On the side of the pressure switch I carefully pushed the paper clip into the port and it just hit plastic, not sure what it's supposed to hit but it seemed like it was solid plastic inside. The result is exactly the same, it kicks on the fan and runs for a few minutes and then shuts off. The ignitor never lights and to the best I can tell nothing ever happens. At the end the LED on the PCB shows an error code that says the pressure switch is open. Any other ideas?

[KC13]

Try this: disconnect flue/exhaust vent from furnace and BRIEFLY run the unit. If normal operation is observed, check flue/exhaust vent for blockage/restriction. If condensing furnace, look for sags in the vent that could be trapping condensate. If unit still fails to operate, pressure switch may have failed.

[rmac18]

Thanks again KC13, same results. Is there a way to test the pressure switch or do I just replace it? Looks to be a fairly expensive part. Or am I just at the point where I need to have someone come out and fix it. I really appreciate the advice.

[rmac18]

Great news, I finally fixed it. I had take apart the metal exhaust pipe and it still didn't work. I left it off for a few hours and then went to put it all back together again and decided I'd try it one last time before putting it in. So I started it up, tapped the pressure switch while it was starting and it worked. So I cleaned the exhaust pipe, it did have some dirt in it and I pushed a broom handle up through it, I'm not sure if there was anything there or not but I put put it all back together and it continued to work fine. Now it's turned on and off 4 or 5 times and seems to be working fine. Thanks a bunch KC13.