testing a capacitor

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=93373
Printed Date: September 13, 2025 at 3:11 AM

Topic: testing a capacitor

Posted By: danthesk8er
Subject: testing a capacitor
Date Posted: April 26, 2007 at 5:21 PM

Hello,
I bought a capacitor on ebay a while back. I'm not sure if it works or not. I just ordered a Kinetik 800 to store some extra power but I would like to put the cap back in as well (to keep voltage at 14.4v likes its suppose to). The problem is I don't know how to test it. I know that you can put a multimeter across it and if it reads the right voltage after being disconnected you should be ok. I tried the microwave capacitor method and it showed that the cap was faulty. I don't know since the microwave is made for a high voltage capacitor if that is different from a car audio capacitor. If you could tell me how to test a car audio capacitor that would be great because I can't find anywhere online that shows how to do it. (side note: the capacitor appears to be in great condition no dents and it isn't blown)
Thanks for your help!

Daniel

Replies:

Posted By: haemphyst
Date Posted: April 26, 2007 at 5:44 PM

OK, first off, a cap WON'T "keep voltage at 14.4 like it's suppose to". Except that it IS "SUPPOSED" to, exactly. Supposed, as in ASSUMED to. It doesn't. Read the second definition, here...

You need an HO alternator, period.

Secondly, "Microwave capacitor method"? WTH is that?

Thirdly, if it's not dented, leaking, scorched... whatever, most likely it's fine. I know of no readily available (EASY) method of testing a 1F (or larger) cap. You COULD use the DeltaT method, but you will only get results as good as your test bench, but it'll at least say "good" or "no good".

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Posted By: aznboi3644
Date Posted: April 26, 2007 at 6:01 PM

yeah...a cap will NOT keep the voltage up

Read this and learn
Why you don't need capacitors

Posted By: xtremej
Date Posted: April 27, 2007 at 10:42 AM

We usually stick them on our tounge it will give you a little zap if its good.....for the microwave capacitor method do you put it in the microwave? If so please video for me posted_image ..

P.S. you probaly don't want to stick it on your tounge we are trained professionals.................

Posted By: KPierson
Date Posted: April 27, 2007 at 6:09 PM

Step 1: Charge it up completely

Step 2: short the leads out.

If sparks fly everywhere then it is good (or at least was).

Of course, shorting it out may damage the cap so you might want to go back to step 1.

Eventually, sparks won't fly, and you can be certain that the cap is bad.

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Kevin Pierson