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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a trane x80 furnace that will intermittently not

Customer Question

I have a trane x80 furnace that will intermittently not ignite. At random I will get a 3 flash pressure switch malfunction but most of the time no codes will flash. I can see the inducer running and the igniter starts to glow. Something then clicks by the civil board and the igniter shuts off while the inducer continues to run. Any ideas?
Submitted: 1 year ago.
Category: HVAC
Expert:  gotoman for ac replied 1 year ago.

How often do you get the 3 flash code. Try cleaning pressure switch first. The hoses that go to the switch inducer housing . Remove them and clean the small fittings where cases attach. Just take a paper clip and insert in fitting a little way. This will clean the opening. Next reattach hoses and retro furnace. Russ

Customer: replied 1 year ago.
Ok so while I was waiting I reconnected power to the unit. The inducer came on, the igniter started to glow and I gave a slight bang to the acces panel door and BOOM, ignition... I'm guessing either I am having a board issue or maybe a gas valve issue? I currently was only getting the call for heat fast flash sequence of blinking, no error codes but also no ignition. Since this is more than likely only a temporary fix, do you have any diagnosis tips for when this happens again? If the pressure switch isn't seeing enough vacuum will it throw an error code, or will it just not activate gas valve? Thank you for the fast response.
Customer: replied 1 year ago.
Also how do I clean the pressure switch? The tube is nice and clear and I will probe the nipple to the inducer.
Customer: replied 1 year ago.
I have found the issue. It is something with the wiring. I can pull on the main harness that goes to the circuit board while the furnace is trying to ignite and get it to work. Which wire could be the issue? Hello?
Expert:  gotoman for ac replied 1 year ago.

Ground wire or thermostat wire. Tighten thermostat wires on terminal board and press all the plugin connectors tight.. Russ