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-   -   AC Unit: Two Bad Capacitors? (http://www.houserepairtalk.com/f8/ac-unit-two-bad-capacitors-6908/)

diyer68 06-22-2009 06:08 PM

AC Unit: Two Bad Capacitors?
 
Bryant 561C

Unit would start and run for 20 minutes or so, even had cold air coming from registers. I first noticed a problem when the registers began putting out warm air. I went to the unit outside and noticed the cooling fan was running, but not the compressor. I stood next to the unit and would occasionally hear a clicking sound like the compressor was trying to start but couldn't.

After shutting it down I turned it on about 30 minutes later. The compressor started, but the cooling fan on top was barely turning...I helped it along with a scewdriver and it spun up slowly - but reached what appeared to be normal operation. NOTE: the fan seems fine...and turns on what feel like brand new bearings...it seemed more like a low voltage or power problem.

I have now removed both capacitors: One is sealed with two wires "Relay and hard start" which was connected to COM and HERM on the larger 3 terminal capacitor 5/40 370 vac.

The 5/40 is bulged on top and tests "open" between all 3 terminals.

I connected my ohm meter to the "relay and hard start" cap and got a reading of 6.8 M ohms. I left the meter connected and the reading keeps going up by about 1 M ohm per minute.

So, my questions are:

Does the "relay and hard start" cap sound like it is ok?

and...If I replace one or both caps, what are the chances there is something wrong with maybe the compressor or something else that is just going to blow these new parts and I am back to square one???

I would appreciate ANY feedback or suggestions! Thanks!

kok328 06-22-2009 07:45 PM

a bulged cap is not necessarily a bad cap. you need a multimeter capable of testing a cap. all other techniques are meaningless. You'll hear people tell you to test the terminals and look for fading continutiy or voltage but, this is not the correct procedure or technique to test a cap and they don't work.
New caps can be had for under $10 ea. so this would be your first cheapest option.
However, I think your condensor fan motor is going bad and allowing to compressor to overheat (internal thermal overload). It will kick back on when it cools down.

diyer68 06-23-2009 06:02 PM

Thank you kok328....

I have replaced both caps and we are up and running well. I am curious though about the running amps I see for the compressor: 10.5, 8.3, and 5.1 for the line connected to HERM. RLA rating is 16.0, so we are well below that, I am more curious about the off balance of 10.5 / 8.3. Also, is it normal to have 5.1 amps at the HERM connection? I thought that may go to zero once up and running.


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