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hello, is the main blower running when 4 appears? and is filter clean?
sorry I lost connection...did you see where I asked if blower is running? This is an overheat trip so before we go to switch I check blower
thank you, ***** ***** not see make or model...but on the front wall of furnace behind the gas valve..do you see a flat plate mounted flush on the wall with 2 wires?
I apologize as I went offline at 11:30.
The picture that came through this morning is of an ac coil not the furnace.
It looks like my colleague has opted out. Do you still need help?
Ok, first I need the model number of your furnace not the AC coil. You can find the furnace model number inside the burner compartment on the rating tag.
Yes an open limit switch will prevent the burners from firing. The limit switch opens if the furnace gets too hot. This can be caused by a dirty filter or maybe blocked heating vents or a clogged AC coil. This error could also be caused by a bad limit switch or a loose connection. On some models there is a flame roll out sensor that's also in the limit circuit which can trip and cause this error. The roll out switch is designed to trip if the burner flame "rolls out" of the burner chamber.
Probably best to call in a pro to check this out. The only thing that's easy to try is to see if the roll out switch(es) (see attached pictures)can be reset. They are located just above and outside the burner chamber. You push the small button between the 2 wires. If it clicks you have reset it. If it doesn't click then it wasn't tripped.