Have a 2 unit system, last week the downstairs unit fan began blowing non stop. Thermostat is set to auto, but when it reaches desired temp it stops blowing cold air, just blows hot. Only circuit breaker stops the fan. Technician came out today and with what seemed like little to no troubleshooting said it's the air handler transformer and wants $200 to replace. Supposed to come back Monday to do so, but nothing I've read about this issue makes that seem like it could be the cause. I have no interest in paying for more and more guesses (which happened this past winter with a heat issue).
Any thoughts on if the transformer can cause a fan to run constantly while the AC functions correctly otherwise? If not, what else could be a culprit?

 

Open the thermostat, disconnect the G wire, and see if that stops the fan. If it does, then may be Thermostat problem, if not, you have other issues, but I don't think it is transformer related.

 

That was the first thing I tried and it did not stop the fan.

 

I agree with clocert doesn't sound like a transformer problem. Can you post model number of furnace and some pics?

 

Ditch that contractor, I doubt it's the transformer,if it failed you most likely would not have any cooling function either,are you sure he said the transformer?
Geo

 

More like a control board issue.

 

The paperwork the tech left says 'low voltage short cause transformer to heat up and run fan all the time- system operational and cooling but transformer needs replaced $151.20'.
I don't know much about AC systems beyond thermostat wiring, but I do have some electrical experience and that doesn't make sense to me.
The system is a Goodman ARUF042-00a1.
I'm hoping they send out someone else on Monday, this guy seemed in a hurry and inexperienced, but I'm trying to figure out what to ask him to check, or what to say when this transformer doesn't fix it so I don't have to pay for multiple parts while they figure it out.

 

Found this on Amazon, there is a picture on Amazon, you can check to see if they match. See customer review.

OEM Upgraded Replacement for Goodman Furnace Control Circuit Board B1370735S



1 customer review



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Ships from and sold by HVAC / IAQ Supply Solutions.





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Most Helpful Customer Reviews


Easy do it yourself
By Brandon on February 21, 2015
Verified Purchase
VERY easy to install. Saved me a ton. My fan was never turning off. The thermostat was unresponsive. This fixed it right up

 

Makes no sense ! Simply cancel the appointment and call a different Co. 2nd opinion can't hurt.
Geo

 

Not a transformer problem. If you have had incompetents working on your unit during heat season (sounds like that may be the case) you may find that they have your back up electric coils coming on constantly and the fan relay safety switch is engaged making the fan run constantly. If so I would hate to see your electric bill..................... if still wired correctly you just need to swap out the fan relay board.