AC capacitor.

[DPEXP]

What is the correct way to check a dual capacitor ?

 

[Heathens]

If its bulged or leaking its bad or use a meter that can read microfarads.

 

[rickairmedic]

Pretty much what Heathens said if the top of it is bulging and not flat and inset into the cap most likely its bad . To test it you need a meter that will read microfareds C= common Herm = compressor and going from common to herm should get you the higher of the 2 numbers . Going from Common to fan ( which is fan LOL ) should get you the lower number either of these are ok if they are within 10% of what the label on the cap says . Most dual caps will say something like 35/5 370 volts. In the example given Herm and common should get you around 35 and fan and common should get you around 5 .


Rick

 

[PrecisionTools]

A capacitor can look OK, measure capacity OK and still be faulty. The best way to measure a capacitor is an ESR meter.

http://en.wikipedia.org/wiki/Equivalent_series_resistance

If you have any friends in electronic repair, especially domestic - TV, Audio etc, then they should have an ESR meter. If you don't know anyone, take your cap into your local TV repair shop and ask if they can test your cap. for you.

 

[hifi_hokie]

http://cgi.ebay.com/Blue-ESR-Capaci...ltDomain_0&hash=item3cba21eaca#ht_1654wt_1004

If you know anyone into ham radio locally, they also might be a good contact for testing electronic components.

 

[Milton Shaw]

Make sure you short the cap terminal to terminal before you touch the terminals. If its good it could be carrying a charge for a week or so and really surprise you.

 

[rickairmedic]

A capacitor can look OK, measure capacity OK and still be faulty. The best way to measure a capacitor is an ESR meter.

http://en.wikipedia.org/wiki/Equivalent_series_resistance

If you have any friends in electronic repair, especially domestic - TV, Audio etc, then they should have an ESR meter. If you don't know anyone, take your cap into your local TV repair shop and ask if they can test your cap. for you.

I have yet to find an air conditioner capacitor that " looked good and tested good that wasnt good " . I suppose in radios and other electronics it is possible but 98% of the capacitors I replace in AC units I can tell as soon as I pull the access panel off the unit that the cap is bad .




Rick

 

[PrecisionTools]

I have yet to find an air conditioner capacitor that " looked good and tested good that wasnt good " . I suppose in radios and other electronics it is possible but 98% of the capacitors I replace in AC units I can tell as soon as I pull the access panel off the unit that the cap is bad .

Yeah, I'm sure your right. Motor control mains stuff is pretty hard on them. I'm just saying that if one looks good and it passes a standard DC charge test but your gut tells you its the same symptoms that a dead cap would give you, then just be aware there are other characteristics to the capacitor that can be measured.

Electrolytic capacitors in domestic electronic equipment would have to be the single biggest cause of failure with them. And a large proportion of those caps will pass a visual & DC charge capacity test.

They are in everything...PC mother boards, networking gear I have even replaced them in automotive ECUs.

 

[DPEXP]

OK so here's the deal, my AC system is about a year old Trane XR 15. one day I noticed the compressor wasn't running so I removed the panel and didnt see anything obvious, I checked the contactor, rang out the compressor windings, rang through the pressure switches and checked the cap with my simpson 260. Everything seemed fine, I reinstalled the cap wiring turned on the system and it worked fine. WTF? 5 months later same thing. I went through the same steps again except this time I installed a spare single cap I had in the garage (similar specs) and got the compressor to run. So I reinstalled the original cap to verify my troubleshooting and of course everything works fine again. So I have a cap on order, Ill install it and go from there. Also all the wiring and terminals look fine. Any other ideas?

 

[rickairmedic]

OK so here's the deal, my AC system is about a year old Trane XR 15. one day I noticed the compressor wasn't running so I removed the panel and didnt see anything obvious, I checked the contactor, rang out the compressor windings, rang through the pressure switches and checked the cap with my simpson 260. Everything seemed fine, I reinstalled the cap wiring turned on the system and it worked fine. WTF? 5 months later same thing. I went through the same steps again except this time I installed a spare single cap I had in the garage (similar specs) and got the compressor to run. So I reinstalled the original cap to verify my troubleshooting and of course everything works fine again. So I have a cap on order, Ill install it and go from there. Also all the wiring and terminals look fine. Any other ideas?

Yes dont buy a Trane next time cause as they say" Nothing runs like a Trane ". The problem is the phrase has a whole new meaning today .



Rick

 

[Alchymist]

To really check a capacitor out you need one of these (top unit):

 

[PrecisionTools]

To really check a capacitor out you need one of these (top unit):

Yep, test 'em with AC and under load...