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johnny67 09-03-2009 10:46 PM

blower won't shut off on new gas furnace
I can't figure this out. I have a 2year old gas furnace. The blower won't turn off and I can't find a switch on the furnace like my old one had that can keep the blower always on or off. The only switch is for the lower cover that shuts it off. I am not familiar with this furnace because it is a house that I rent to tenants. I tried an old school t stat and a new digital one with the same results. There are only 2 wires coming from the circuit board right now. The only time it shut off was when I raised the heat and then it turned on again and stayed on. The heat works fine. Is there a switch that I am not seeing on the furnace?

Plumber101 09-03-2009 10:53 PM

How many wire are connected at the thermostat?

Also post brand and model of furnace

johnny67 09-03-2009 11:01 PM

2 wires at the t stat. I am not sure what model it is because I am not at the house but if this helps it is a 80+ AFUE upflow/horizontal furnace with no A/C.

Plumber101 09-03-2009 11:03 PM

Where is the furnace installed? Basement, attic...where?

johnny67 09-04-2009 04:35 AM

It is in the basement.

beenthere 09-04-2009 05:10 AM

Probably has a dirty/plugged air filter. And the limit switch tripped when they ran it for heat on a cool night.

biggles 09-04-2009 07:17 AM

fan ON limit disc might be closed shut.the FAN during heating cycle is 100% isolated from the stat action or call.the actual heating of the heat exchanger or a time delay on the furnace solid stae board(fan relay) runs's either that disc or the relay on the board is arced closed...tap the relay on the board with a small screwdriver handle see if it opens.if you have the stat in hand with just the subbase wired looking at it the fan closure to run is in the furnace limiting wiring.when the furnace is called for the HEAT-X gets hot and the supply fan comes ON when the stat is satisfied the gas shuts off and the HEAT-X cools down and that disc should open shutting off the fan.

johnny67 09-05-2009 01:35 AM

The filter was very dirty, I put a new one in now. Is there any other clue you guys can give me to know what to look for when looking for the relay to tap on. I will be at the house tomorrow and I will note the make of the furnace and take a few pics of the electronics board etc.. thanks

biggles 09-06-2009 07:09 AM

the relay on a solid state board is about 1" x 1/2" in size even though the stat isn't calling it the contacts might be be swinging open when the control voltage is stopped.

johnny67 09-06-2009 05:32 PM

The furnace is a Nordyne model #FG6RA 072C-12A. I took a picture of the board and I was told by the installer that it is probably due to the clogged filter just like you guys said and that the limit switch needs to be replaced. He said that the part is $25 and he could come down and put it in plus a $100 service call. Is this something a handy guy like me can do. I have experience with electrical work. Or is this something left to a professional? I did tap on a few of the black boxes in the pic but it did not turn the fan off (not sure which one was the relay switch)

JohnH1 09-06-2009 06:24 PM

Its not a open limit. You said the heat started and ran fine. If it was a limit the burners would not run. The only thing I could think of is a bad board.

johnny67 09-06-2009 06:30 PM

thats right. When I turn the heat up the fan will shut off for about 10 seconds then it will kick on again with the heat. Although I am not sure if I have let it run the cycle yet since the days around here have been hot, but I can try that tomorrow.

JohnH1 09-06-2009 06:33 PM

I am also not thrilled with the copper gas line. Gas and copper dont play well together. :no:

Plumber101 09-06-2009 06:55 PM

Check the limits that are on the blue wire. There is one right up front and one that is by the blower. They should be closed circuit. They also had a manual reset. The button in the middle of the connector. Just a thought to see if one has tripped.

beenthere 09-06-2009 07:01 PM


Originally Posted by JohnH1 (Post 324571)
I am also not thrilled with the copper gas line. Gas and copper dont play well together. :no:

Natural gas, and copper are fine together.

Its the acid that some of the companies don't remove that is a problem.
Some areas certify their gas to be acid free.

His may be one of those areas.

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