Carrier furnace 394GAW000050


Old 02-26-20, 02:09 PM
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Carrier furnace 394GAW000050


I've hopefully narrowed this down pretty far and that a more trained brain than my own can push us across the finish line. :)

The details:
- Carrier furnace 394GAW000050
- ecobee3 thermostat
- Has run properly for years (furnace heats, blower turns on, blower turns off when heating is done)
- Now the blower runs continuously, regardless of whether the furnace is heating
- No G-wire, so this is not controlled by the ecobee (according to what I've been told)
- Replaced limit switch which didn't change anything (not to say that couldn't still be it if it was a faulty replacement, but...)

Photos attached. Please let me know if there are any more details or photos I can provide. Thanks!
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Old 02-26-20, 07:51 PM
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Welcome to the forums.

Has run properly for years
That furnace is 40 years old...... has it been cleaned and professionally serviced ?
Manufacturer recommends every year. Every other year is ok.
The heat exchanger needs to be checked for cracks and rust thru.

Is this a standing pilot light or intermittent ignition ?

394GAW manual (pdf)

Old 03-01-20, 06:16 PM
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Don't spend another cent on that furnace - it's around 60% efficient and probably has a cracked heat exchanger.

The flex gas line in the cabinet is illegal.

Likely a sticking relay on the control board but would have to be diagnosed before changing the part, and as stated above that furnace isn't worth fixing. the board is probably not even available any more.

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