No power to the Vent motor

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Old 11-10-13, 04:08 PM
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No power to the Vent motor

I changed out the board, transformer, thermostat and checked all wiering 4 x

I even put the old board in a different unit and it worked fine!!!

I checked the continuity of the vent motor wires and was fine.
for some reason there is no power going to the vent motor.

When I turn the system on and call for heat the led is on solid then after about 10 seconds it blinks 2x stating that the pressure switch is not working but that is because the vent motor does not come on.... HELP!!!
 
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Old 11-10-13, 06:04 PM
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Did you check for 120vac at the board on the connections for the vent motor ?
 
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Old 11-10-13, 06:11 PM
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Yes, I checked the wies that connect to the vent motor - no Power.
I cheched for continuity of the vent motor wires - good.
I checked for power at the connections on the board - no power.

What is going on?!
 
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Old 11-10-13, 06:29 PM
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When you checked for voltage at the control board terminals for the vent motor was there a call for heat?
 
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Old 11-10-13, 07:23 PM
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Try disconnecting the pressure switch to see if the venter then starts or at least you get 120 volts to the terminals. On some furnaces, if the board senses a closed pressure switch at a call for heat but before the vent motor starts, you will get a pressure switch code.
 
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Old 11-10-13, 08:30 PM
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Fired: As far as i can tell there was a call for heat then the led started flashing 2x

Grady: Thanks for the info, I will give that a shot tomarrow and see what happens.
 
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Old 11-12-13, 09:58 PM
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Grady, That was it, thanks so much.
I disconnected the pressure swith and it came right on.
I should have figured that was it but duh!
Thats why I came here, knew someone would have the answer.
I switched out the pressure switch now and all is right in the world again!
Thanks.
 
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Old 11-13-13, 06:45 PM
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Rarely do pressure switches actually fail but they are not failure proof. I'd bet an easy 95% of the ones replaced don't need to be. A few boards will actually give a different code if the pressure switch is closed before the venter starts. Glad you got it fixed.
 
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Old 11-13-13, 06:51 PM
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That's interesting. Usually most boards will give a different code if the switch is prematurely closed.
 
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