Questions about a Motor Starting Capacitor

My garage door opener stopped working; it just hummed for about 2 seconds. For no particular reason I touched the starting capacitor and fixed it. It ran okay for a couple days, then stopped. I touched it again and it ran twice before breaking. Now my magic touch fails completely. (I can't find any loose wires) The manufacturer's best guess is that the capacitor is bad.
It takes a 53-64 mfd 220vac 30b0363 Fujitsu Towa no. gk-86
1) Any way to varify the capacitor is bad before replacing it? I put an ohm meter across it, and it shows an open circuit, but since I have never tested a good capacitor I don't know how much that proves. 2) The manufacturer wants $20 for a replacement. Am I likely to find one cheaper locally? Where, an electrical distributor? 3) There are two red wires going to one contact and two blues going to the other. Is a capacitor symetrical, so if I got my contacts backwards it would be okay?
Thanks
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toller wrote:

Capacitor tester.

Don't know about where you are, but you could buy one online. http://www.surpluscenter.com/item.asp?UID 05020613094239&item"-1204&catname=electric

No, it would NOT be OK. The capacitor is polarized.
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Thanks, I needed that.
<G>
== Use an ohm meter......with the zero set to the center of the scale, the needle will swing one way, then it return to center. On reversing the leads, it will swing the other way twice as far, before coming back to center.
Otherwise, the capacitor has most definately failed.
--

SVL





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Travis Jordan wrote:

I should have said "IF the capacitor is polarized". Some motor start capacitors are non polarized. Check to see if the contacts are labeled + and -. If the capacitor is NON polarized, then it won't matter how the wires are connected.
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Thanks, $129 is a bit better than $20. For that price I can gamble. This capacitor has no markings on it, so I guess it is non-polarized. On a polarized capacitor, do the red or black wires go to +?
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toller wrote:

By convention, the red wires would connect to +.
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A cap rated for AC use (as that one is) ain't gonna be polarized.
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More inserted.
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check for cold solder joint or bad connections first.
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My parts house had start caps,a nd run caps. Start caps were about $5, and run caps are about $20. I'd suggest the one from the fan company. More likely a run cap. Start caps are used on compressors like in refrigerators.
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Hi Stormin, hope you are having a nice day
On 09-Feb-05 At About 22:18:58, Stormin Mormon wrote to All Subject: Re: Questions about a Motor Starting Capacitor
SM> My parts house had start caps,a nd run caps. Start caps were about SM> $5, and run caps are about $20. I'd suggest the one from the fan SM> company. More likely a run cap. Start caps are used on compressors SM> like in refrigerators.
You really should get more training. start capacitors are also used on quite a few motors.
-=> HvacTech2 <=-
.. URA Redneck if you hold a frog and _it_ worries about getting warts.
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