# Capacitor checks



## erics37 (May 7, 2009)

I have a basic Fluke multimeter (a 115 or 117 or something) and it has a Capacitance feature. It's dead simple; it tells me the capacitance, I compare it to what the label on the capacitor says, and it's either no or go. Pretty handy for single-phase CS or CSCR motors.

You can also charge it up with a megger and see how long it takes to discharge itself.

Alternatively, you can throw it like a hand grenade and then tell the customer it's no good and just get a new one.


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## Big John (May 23, 2010)

If you pick the megger route: Be mindful of the capacitor working voltage, I know a lot of meggers have a 250V minimum setting.

-John


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## J Corrin (Sep 7, 2007)

My fluke does not have the capacitence value on it. By the way, it is not for a customer, it is on the A/C unit on my camper. LOL


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## dronai (Apr 11, 2011)

Measure the Farad reading, and compare to the listed amount on the capacitor.


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## erics37 (May 7, 2009)

J Corrin said:


> My fluke does not have the capacitence value on it. By the way, it is not for a customer, it is on the A/C unit on my camper. LOL


Well you wanted to know the proper way to do it. In that case you'd need the proper meter.


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## Theriot (Aug 27, 2011)

I have had some that the meter on cap showed it was good but still didn't work. I had an old timer show me that what he would do was ohm it with a meter and you can see the ohm going up and then it would drop and cycle again to show that it's firing. Has anyone else heard of this?


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## mrmike (Dec 10, 2010)

Theriot said:


> I have had some that the meter on cap showed it was good but still didn't work. I had an old timer show me that what he would do was ohm it with a meter and you can see the ohm going up and then it would drop and cycle again to show that it's firing. Has anyone else heard of this?


 
This is how we always made a quick check of them in the plant I worked in.........................we used an analog meter, as most of us carried both, for various reasons like this one...................


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## wildleg (Apr 12, 2009)

capacitor goes bad shorted or open. if it's shorted then it's obviously bad. if it is sizable enough, and your meter isn't too spastic, you can watch it charge with the meter, and know it is good. tiny ones charge too fast for you to see it charge.


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## wendon (Sep 27, 2010)

If it's a run cap you can also give it a go/no go test by running the unit and checking the amp draw on the run cap wire. The best way is to make sure the cap is discharged and then test it with a cap tester or a meter with that function on it.


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