blower wont start - replaced motor and capacitor still wont start

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Old 05-13-13, 07:44 PM
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blower wont start - replaced motor and capacitor still wont start

im at a loss what to do next.

tempstar NTC6125KJG1 furnace. blower not turning on when thermostat calls for it. replaced blower motor and capacitor. when zone controller activates fan circuit, fan led comes on on the zone controller, i hear the capacitor charge up and a relay click but motor does not start. honeywell ST920C-4507 fan control board - I've already spent $$ on the motor and cap, i don't want to buy more parts without trying to troubleshoot the fan control board - how can i isolate the fan control board from the zone controller and thermostats to see if thats the problem? what should i test?
 
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Old 05-13-13, 09:42 PM
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I would think that the board is not sending voltage to the motor when it should. Have you verified this with a volt meter? Have you removed the board to look for a burn mark on the back? Jumpering R to G would normally call for fan operation.
 
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Old 05-13-13, 09:49 PM
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I removed the board and sure enough there was a burn on the back!

It looks like I replaced the blower motor for nothing.

Why do these Honeywell boards burn like this? It appears to have burned below a relay.

Is this a common problem ?
 
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Old 05-13-13, 09:52 PM
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its a common problem on all manufacturers boards..... Usually caused by motor over-amping or a defect in the circuit on the board.
 
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Old 05-13-13, 09:55 PM
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Ok thanks I guess I will need to get another board tomorrow
I sort of regret replacing the motor and cap now but the other one was 11 years old maybe time to replace it anyway I guess
 
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Old 05-13-13, 09:57 PM
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Many pc board issues are caused by lack of a quality solder job from the board supplier.

Keep the motor and cap for a working spare.
 
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