I have a 20 year old Goodman furnace. The last two weeks I've just started to use the heat again and noticed that the unit will sometimes run for 10 minutes or so, shut off, then start again after 3-5 minutes. The first thing I checked was my filter and threw a new MERV 8 in just to be sure. That didn't help. So I read online that a dirty flame sensor could potentially cause this as well. I climbed up into my attic tonight and did this:Turned off power switch to furnace.Flipped gas valve to 'off' positionTook out flame sensor being careful not to touch it with my fingers. Cleaned it off with some 000 steel wool and reinstalled.Turned gas valve to 'on' position.Turned furnace power on.Turned thermostat up to test it.Now it will not light. The fans kick on for 10 seconds, then the igniter glows red hot for 5 seconds or so, but I never hear the gas valve click open. It cycles like this 3 times before shutting off and locking me out. I've checked all connections are good, that the ground to the gas valve is good, and the command signal is sending 10.2 volts to the gas valve. I even tried tapping on the valve lightly with a wrench to see if the gas valve was stuck.Would the flame sensor have ANYTHING at all to do with this? My thought was that it should at least light and then turn off after a few seconds if my flame sensor cleaning went poorly. Every time I looked at the control board LED it was solid red. I'm going to try watching the LED for the full cycle now to see if it flashes for a trouble code... via /r/DIY https://ift.tt/2SZmnYr
