Air Handler fan won't turn off


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Old 04-17-10, 09:35 AM
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Air Handler fan won't turn off

I have a Trane Weathertron heat pump with a American Standard air handler under the house. Everything works fine, except the air handler fan never stops no matter what settings are on the thermostat. I can trip the circuit breaker to the AHU and I can hear the relays click. When I measure the contacts with a volt ohm meter the contacts measure open, as they should per the schematic. I can disconnect the green wire, coming from the thermostat, at the printed circuit board (that is hooked to the relays) and it has no effect. Motor still won't turn off. The AHU part number isTWH042B140A. Thanks for any help that you can provide.

Mark
 
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Old 04-17-10, 11:07 AM
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Is there anyway to bypass the fan timer circuit board (mine is plugged into the relays so it can be easily removed) to verify the relays are working. I would think that if I could bypass the fan timer circuit board, everything should work, except the AHU fan will not stay on for a few seconds after the compressor turned off. Here is a product sheet on my Fan timer and relay unit http://s3.pexsupply.com/manuals/1257..._PROD_FILE.pdf .

Thanks again,
Mark
 
 

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