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New control board is turning on the compressor and not the fan

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gemini28
gemini28 Member Posts: 2
in Thermostats and Controls
I have 2 furnaces in my house, both Trane XE78. One of them needed a new control board, a White-Rogers replacement. Now when I go to turn on the fan to circulate air through the house, the compressor fan outside turns on instead. I've compared the control boards in both furnaces and the wires are not all connected to the same ports.
The old furnace board wires are as follows:
Cool - black wire
Heat - blue
Park - red
Park - yellow
Line - black
XFMR - black

The new furnace board wires are:
Cool - black wire
Heat - blue
Park - yellow
Fac - red
Line - white
XFMR - black

My question has to do with the red wire. There is another Park port on the new board and I'm wondering if the red wire is simply on the wrong port, the Fac port. I'm afraid to switch it, though, because I don't want to short out the board and have to buy a new one. Can anybody help?

Comments

  • Dan Foley
    Dan Foley Member Posts: 1,258
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    G is back feeding through the thermostat to Y. Check low voltage wiring at control board and thermostat.

    Isolate Y on the control board or install isolation relay.
  • hvacfreak2
    hvacfreak2 Member Posts: 500
    edited April 2016
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    I believe the terminal designations that the o.p. listed are line voltage connections to the board for power and fan speeds. It looks like the low speed red wire just needs a park ( unused ) terminal. If nothing is available just tape it off as to isolate it. Do not use the EAC terminal for a fan speed connection , that red wire does not belong there.

    The terminal labled " line " needs to be 120 vac HOT , whatever color that is so be it.( Edit : it looks like both the line AND xfmr may require 120 vac HOT ). Be careful and good luck !!!
    hvacfreak

    Mechanical Enthusiast

    Burnham MST 396 , 60 oz gauge , Tigerloop , Firomatic Check Valve , Mcdonnell Miller 67 lwco , Danfoss RA2k TRV's

    Easyio FG20 Controller

  • Firecontrol933
    Firecontrol933 Member Posts: 73
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    Your problem is with the low voltage wiring.
  • gemini28
    gemini28 Member Posts: 2
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    Thanks guys! Got it all working with your help!

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