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-   -   Trane Outside fan stopped working - cap or relay? (

JAWyrick 07-12-2011 08:51 AM

Trane Outside fan stopped working - cap or relay?
Hello to Everyone!

I have a Trane central air unit that suddenly stopped cooling yesterday. I walked outside and noticed that the fan wasn't working. (circulation blower still ok). I turned the power off for about 20 min and inspected the panel housing the start caps and relay. I tried to power back up and same thing - compressor attempts to come on(you just hear the loud buzz of the power being applied) but fan won't kick on. I pulled the power disconnect from the outside box and then put it back it. This time the fan kicked on as it normally should and it's seems to be running fine again. It has ran from 6PM yesterday and is still running fine this morning.

My question is - what would have caused it to momentarily stop working?

I suspected a failing start capacitor. Just this time last year the large main cap for the compressor failed so it seems reasonable due to age. I haven't pulled the cap out and checked the capacitance yet though I'm not sure that a simple capacitance check will tell whether the cap is still fully healthy or not. I checked the voltage on the relay and got 24V at all points. Is it possible a relay contact could have failed? This did happen during the hottest part of the day.

That's really about the extent of my knowledge on what may have caused the fan to not turn on. I'm posting here to see if anyone has any opinions/experience they wouldn't mind sharing in case there is something else that I'm not aware of. To my knowledge this is the first time this particular problem has ever happened. The unit is ~15years old.

Thanks & Best Regards


cascadehvac 07-12-2011 10:33 AM

it is possible there could be problem with a capacitor. but typically they work or dont. the contactor way be going out and not consistently making the connection to start the equipment. look at contactor and check to see if connections are badly pited.

JAWyrick 07-12-2011 11:03 AM

Good point. When checking for pitted or worn areas are you referring to the area beneath each screw terminal where the spade connectors make contact? I'm not super familiar with these - are the switching contacts fully visible from the outside?

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