Hello, I have problems with my furnace. It is York G8C model and model number is G8c07516muc12g. I have been using this furnace for about 15 years now. I’ve had a problem with this furnace about 7 years ago, and it was repaired by replacing circuit board. New problem started from about three weeks ago. Furnace stopped working and there was error sign on the board. 3 red blinking flashes - Pressure switch failed to close. I restarted the furnace and found that ignition didn’t start at all after inducer pan started to operate. 3 flashes appeared after several clicking sounds and furnace stopped operating in few minutes. So I tried - turned off the power - Cleaned up the inside of furnace. - Checked and replaced the air filter. - Checked the pressure switch tube and cleaned inside. - unplugged the pressure switch wires and plugged it back. - used paperclip to clean the nipple on the inducer pan - checked the ignitor (it looked bit dirty.) - There is no condensate pipe for my furnace, so I cannot check clogged pipe. Nothing worked. Based on technician's advice, I ordered new pressure switch and ignitor, and replaced them. OK it started to work again after trying resetting the furnace several times, but it lasted only for 2 days and stopped working again. This time the error sign was 4 flashes - limit switch open. I turned off the furnace, cooled down, restarted, and it didn't even start to ignite it and showed limit switch error sign. After that, it just blowed cold air for several minutes and stopped operating. Strange thing is that if I unplug all the wires on the circuit board, reconnect them and restart the furnace, then it starts to ignite the flame and run normal for 5 to 10 minutes. After then, Fire's gone, 4 flashes appear, and it starts to blow only cold air. If I let it go, it will stop operating eventually, and tries to restart after couple minutes, but it doesn't even start ignition by itself. The only way I can start to fire up is unplug the wire, reconnect them back to the circuit board and restart it. Then it runs for about 10 minutes, fire disappears, 4 flashes error and blows only cold air. I tried to clean the flame sensor with steel wool, but it didn’t fix the issue. Now it even stopped making fire at all. Current symptom is that it shows random 3 (Pressure switch failed to close) or 4 flashes (Limit switch open). If I power on the furnace, it starts with green flash (normal status), inducer motor starts, flash changes to orange light with slow blinking (sign when it is normally operating), ignitor starts to glow, can hear clicking sounds several times, but it doesn’t start fire up, ignitor stopped glowing, and orange light changes to red error blinking flashes. 3 or 4 flashes randomly. Rarely, it shows 6 flashes as well. Or It just starts to show 3 or 4 flashes right after I power on the furnace. In this case, there is no ignitor glowing at all. I checked a limit switch and 3 roll out switches with multimeter, it all showed closed status when power is off. I also tested pressure switch with multimeter. Pressure switch was opened status when there is no pressure, and it closed when the inducer motor starts blowing. I don’t know any other way to test the switches now. I tried to bypass the limit switch for testing, and fire started. So I replaced the limit switch, but it doesn’t fix the problem. Same 3 or 4 flashes. Do you think it might be a circuit board problem? Thank you so much in advance.

Hello, New to this forum! I've been having an odd issue recently. My oil furnace will turn on for a minute or two a few times per day, despite none of my thermostats saying that they are in heat mode. Is this normal? First time owning a home with a furnace and not overly familiar with them. Mentioning this as I'm not sure if this has been an issue prior or may be something that has only occurred since: I recently replaced my 2 battery operated thermostats (2 wires, black and white) with newer Honeywell wifi thermostats and ran new 18/3 wiring for them, patched into the existing wiring at the very end and confirmed both are wired correctly working fine during heat cycles. The furnace is an older NY Thermal oil ignited model that supplies hot water based heat to both my basement and upstairs. Each theromstat controls one level using motorized valves on the outbound piping and was all in place when I bought the house just over a year ago (its an older partially renovated 1930s home that I am working to get done in my spare time) Any suggestions on what may be causing this and what I should check?