Furance is a Trane XE70. Original boad went intermitent shut-down. Swapped to 843. Green light running. When it's on auto furnace kicks on, fan does not.In about 90-120 seconds I then think it thermals and shuts off. Works perfect with the fan on manual on mode. Is there a fan turn on wire I am missing? Any help appreciated.

The 50E47-843 is the replacement suggested by White-Rodgers. You have possibly disonnected a fan control wire, you may have a bad fan control, or the heating speed on the motor could be bad. If you can provide a wiring diagram of the furnace we can probably help you track down the problem.

Did a short jumper wire come with the new board?
I replaced a board on a Trane furnace (unfortunately, different board number) and needed to jumper between RO1 and RO2 on the 12-pin connector.

Consult the installation instructions to see if this might apply to your board.

Good luck,
WallyH

No 12 pin connector on this module.

I decided to mess with this again. Auto fan works with AC, but not with the furnace. Isn't a thermostat in charge during AC only? What controls the fan turn on in auto furnace mode.

Quote:

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Originally Posted by Grady White

The 50E47-843 is the replacement suggested by White-Rodgers. You have possibly disonnected a fan control wire, you may have a bad fan control, or the heating speed on the motor could be bad. If you can provide a wiring diagram of the furnace we can probably help you track down the problem.

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How would I get you this diagram? The rogers-white tech guy said there is no turn on wire for this module. I didn't end up with any loose wires, all were transferred over per their diagram/conversion chart.