Lennox G43UF fan won't shut off.

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Old 05-26-13, 10:56 AM
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Lennox G43UF fan won't shut off.

I have a Lennox G43UF Furnace and a White/Rogers Tstat. In Heating or Cooling auto-mode the fan runs continuously. Tried turning the system switch to "off" on the Tstat - fan continues to run. Only way to stop it, is by turning the main power off at the furnace. I've tried disconnecting all the wires at the Tstat to see if that's the problem - no fix! I can only find one fuse on the furnace circuit board and it's ok.
 
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Old 05-27-13, 08:45 AM
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At the furnace control board remove the wire from the G terminal. DO you have any error codes from the control board?
 
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Old 05-27-13, 09:00 AM
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I removed the white wire from the G terminal... The fan does not run now and no error codes if you are referring to the flashing green/red lights - there is a simultaneous slow flash of the red/green. There is a faint hum when the cover safety switch is pushed in.
 
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Old 05-27-13, 09:13 AM
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This indicates that there is a short in the wiring if the fan still ran with the wires removed from the thermostat but now it does not continue to run with the wire removed from G at the control board. White is not typically the color used for G but there is no universal color code for low voltage wiring. You need to replace the wiring from the furnace to the thermostat or if you have extra wires in the cable then you can try using it for G . You would have to change the wire at both the furnace and the thermostat.
 
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Old 05-27-13, 09:28 AM
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Thanks for your help... a Tech. has been called I'll post his fix for further reference.
 
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