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    air0mjb's Avatar
    air0mjb Posts: 3, Reputation: 1
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    #1

    Oct 25, 2012, 02:44 PM
    Fan motor on HVAC will not turn off.
    The diagnostic light blinks 6 times since I replaced the circuit board that a HVAC tech said was bad. Apparently that was not the problem it still stays on. I have replaced the therostat with a new one. The T/S chart says it's a 115 VAC polarity problem or a grounding problem. How do I know? Nothing has changed with the plug for a ground. Does the thermostat have anything to do with the polarity of something? Mike
    T-Top's Avatar
    T-Top Posts: 1,871, Reputation: 100
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    #2

    Oct 25, 2012, 07:05 PM
    The make and model of the furnace will be a big help. If a leg of power was reversed in the process of changing the control board or working on that code will show up. Is this a system that has two units twinned together?
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    air0mjb Posts: 3, Reputation: 1
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    #3

    Oct 25, 2012, 11:12 PM
    It is a Trane XR80. No this is a single unit. The fan ran before changing out the control board. It still runs after the board change so I am confident the board didn't have an effect on the fan problem. I think I have 2 different problems but I am not an HVAC tech. Thanks for helping so far. Mike
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    #4

    Oct 26, 2012, 02:38 PM
    Quote Originally Posted by air0mjb View Post
    It is a Trane XR80. No this is a single unit. The fan ran before changing out the control board. It still runs after the board change so I am confident the board didn't have an effect on the fan problem. I think I have 2 different problems but I am not an HVAC tech. Thanks for helping so far. Mike
    Did you try to reverse polarity of the power going to the furnace to see if it gave the same code?

    Trane XR80 furnace provides a LED on its integrated furnace control for quick diagnostic. Here is its diagnostic code:

    LED Flash Error
    Flashing Slow Normal No Call for Heat
    Flashing Fast Normal Call for Heat
    Continuous On Replace Control
    Continuous Off Check Power
    2 Flashes External Lockout (Retries or Recycles Exceeded)
    3 Flashes Pressure Switch Error
    4 Flashes Open High Limit Device
    5 Flashes Flame Sensed when NO flame should be present
    6 Flashes 115 VAC power reversed polarity or poor grounding
    7 Flashes Gas Valve circuit Error
    8 Flashes Low Frame sense Signal
    9 Flashes Check Ignitor
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    air0mjb Posts: 3, Reputation: 1
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    #5

    Oct 27, 2012, 02:48 AM
    I have the diagnostic chart. The unit is 4 years old and was running fine until the fan kept running. If the circuit board is fine and now the light blinks 6 times why would changing the leads on the plug fix the problem? I didn't touch anything with that. What ground are they talking about? Would it be in the power cord. I have a 1951 house and there is no grounds through the outlets. It's a 2 wire system, but it was hooked up like that for 4 years with no problems so how could it be a grounding problem?
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