Questions about a Motor Starting Capacitor

Posted by toller on February 6, 2005, 9:48 pm

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

Posted by Travis Jordan on February 6, 2005, 10:13 pm

toller wrote:

> 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.

Capacitor tester.

> 2) The manufacturer wants $20 for a replacement. Am I likely to find
> one cheaper locally? Where, an electrical distributor?

Don't know about where you are, but you could buy one online.
http://www.surpluscenter.com/item.asp?UID=2005020613094239&item=22-1204&catname=electric

> 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?

No, it would NOT be OK. The capacitor is polarized.

Posted by Travis Jordan on February 6, 2005, 10:12 pm

Travis Jordan wrote:

> toller wrote:

> > 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?

> No, it would NOT be OK. The capacitor is polarized.

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.

Posted by toller on February 6, 2005, 10:24 pm

> Travis Jordan wrote:

>> toller wrote:

>> > 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?

>> No, it would NOT be OK. The capacitor is polarized.

> 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.

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 +?

Posted by Travis Jordan on February 6, 2005, 10:26 pm

toller wrote:

> 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 +?

By convention, the red wires would connect to +.

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