Hello all,
I'm having a problem with my central air unit. The low voltage coil in the contactor in the condensing unit outside keeps shorting out. I've had to replace the contactor(outside) and the control transformer(inside the furnace) a couple of times already. I've checked voltage and it seems to be correct. Could anyone tell me why the 24volt coil keeps shorting out?
Thanks,
Joe.

 

Hello all,
I'm having a problem with my central air unit. The low voltage coil in the contactor in the condensing unit outside keeps shorting out. I've had to replace the contactor(outside) and the control transformer(inside the furnace) a couple of times already. I've checked voltage and it seems to be correct. Could anyone tell me why the 24volt coil keeps shorting out?
Thanks,
Joe.

if the coil is exposed to high temperatures then its isolation melts and it shorts.

 

mik3,
Thanks for the response, This is the original condensing unit (prolly 8yrs old) the contactor is isolated in it's own compartment, sheilded from the compressor and fan motor heat. I dont think ambient heat is the culprit here. If thats what you're inferring.
Thanks again.

Joe.


(Like minnows in a bucket...)

 

What about condensation? Is the contactor getting wet?

 

Does the VA of the replacement transformer match the original? When you measured the voltage at the transformer was it while it was under load?
Ed

 

I doubt it . It's a sealed unit. I've got to take the top panel off to get the back panel off just to get to it, but I will check it tomorrow to see if there's any excess gaps ...maybe where the wiring comes in.

Thanks,
Joe.

 

Does the VA of the replacement transformer match the original? When you measured the voltage at the transformer was it while it was under load?
Ed

Yes it's a 40 va, same as the original.
When I checked the 24v it was under the load of the furnace blower.
120v.into the transformer-24 out.
230v line voltage outside. 24v. at the wires going to the coil.