Help with furnace.

Old 10-16-09, 12:32 PM
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Help with furnace.

I have a Trane high efficiency gas furnace, about five years old. The heat cycle comes on but after it is done the fan (not the exhaust, the blower fan) does not shut off and after that the heat doesn't come back on. I have to turn the power off to the furnace to get heat back. Does anyone know why this might be happening, thanks?

Old 10-16-09, 12:58 PM
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It might be high limiting (furnace heat exchanger getting too hot inside).

Causes can be a weak limit switch, adjusted wrong(if that is even possible)limit switch, plugged furnace filter, too many closed down dampers on the ducts or registers in the rooms, or blocked cold air returns, or blocked secondary heat exchanger due to someone leaving out a filter or incorrectly installed filter, or blocked A/C coil fins above the furnace (if you have central air), or a blower that is not as efficiently moving the air due to faulty motor or caked dust in the curved fins, or gas pressure too high- too big a fire.
Old 10-16-09, 04:55 PM
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A Trane furnace that is only 5 years old should have a blinking LED that can help determine the cause of this problem.

Here are some examples...

Trane TUX


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