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-   -   HVAC - almost made it through the summer (http://forums.pelicanparts.com/off-topic-discussions/627680-hvac-almost-made-through-summer.html)

gr8fl4porsche 09-01-2011 01:03 PM

HVAC - almost made it through the summer
 
Still hot in St. Lou

102 today - summer is not over yet.

AC crapped out last night

Compressor was humming and condensor fan would not spin and motor was very hot.

So I changed out the motor and capacitor. Here is the result when I flipped on the thermostat. New capacitor appears to have blown instantly.

http://forums.pelicanparts.com/uploa...1314909738.jpg



Wiring at compressor looks good. Unit is 6 years old.


http://forums.pelicanparts.com/uploa...1314909803.jpg

Old capacitor was dead and had similar discoloration near the compressor post like the defect in the new one.


http://forums.pelicanparts.com/uploa...1314909880.jpg

Would a locked up compressor burn out a new capacitor like that or did I wire the replacement motor wrong.

Wires from motor (AO Smith)
Black wire to left side of contact switch, yellow wire to right side (the side with the pull), brown to 'fan' on capacitor and brown/white to to 'common' on capacitor.

I checked that the capacitors are similar.

turbo6bar 09-01-2011 01:27 PM

Use a multimeter to check if you compressor is grounded. Remove the black, red, and orange, and check each to ground. If any shows less than 10 ohms, your compressor is toast.

However, you say the compressor was humming, so it sounds like it may be working. Did you get the right cap to match the new condenser fan motor?

You're shorting out somewhere, but the condition of the compressor terminals suggest the problem is not the compressor itself.

gr8fl4porsche 09-01-2011 01:47 PM

I will check in the morning concerning the match between the new motor and new cap.
The new cap matches the old one and the Johnstone rep had my new motor info when he picked my new cap. Will double check.

I am heading out to check the compressor leads.

gr8fl4porsche 09-01-2011 03:16 PM

On compressor

C to R = .001
C to S = .002
S to R = .003

Looks good

Found a good ground and received no readings on any contact via my cheapo multimeter.

I assume thats a good sign?

MBAtarga 09-01-2011 04:07 PM

Quote:

Originally Posted by gr8fl4porsche (Post 6230959)
On compressor

C to R = .001
C to S = .002
S to R = .003

Looks good

Found a good ground and received no readings on any contact via my cheapo multimeter.

I assume thats a good sign?

It means it wasn't shorted out by a lightning strike like the compressor on my basement unit's heat pump was last spring!

billybek 09-01-2011 04:41 PM

Good sign no shorts to ground but if your measurements are accurate and represents ohm value from winding to winding, you have a bit of a problem.
Interesting enough, they do add up. Run to common + Start to common should equal Run to Start.
Did you take these readings with all the wires off the terminals at the compressor?

gr8fl4porsche 09-01-2011 04:48 PM

Yes wires were off compressor. Multimeter is very cheap - probably not very accurate. Will test in the morning with a better unit. Anything else to test?

billybek 09-01-2011 05:23 PM

No not yet. Just recheck the compressor motor and the condenser fan motor.
I never liked those capacitors that do both condenser fan and compressor.

turbo6bar 09-02-2011 04:17 AM

Those readings, if in ohms, seem really low. My low-end Fluke doesn't read ohms to three decimal places. It's been a while since I read ohms across the terminals. I recall numbers around 3 to 5 ohms, though???

If the terminals aren't grounded, I think you are safe. Check the wiring to ensure there is nothing shorted.

rick-l 09-02-2011 06:05 AM

He is probably reading 0.001 kilo ohms or 1 ohm and probably not very accurately.

gr8fl4porsche 09-02-2011 07:33 AM

Thanks for the help gentlemen!

House is cooling nicely.

I ended up installing separate caps. The new motor did not like the dual cap.


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