Motor Run/start up Capacitor - Replacement

[tmcw]

Anyone know much about run caps in motors?

I have a vacuum pump that was having trouble starting, you had to flick the fan to get the motor running, and was wondering if the specs on the old cap and a new one are close enough of a match to be ok.

I've attached a photo of the 2 side by side, the one on top is the original one.

Will I be ok replacing it with the one on the bottom?

Are there any differences in the specs that would be of concern?

[Andrew F. Ali]

Re: Motor Run/start up Capacitor - Replacement

No. Nothing to worry about. The important thing is the 4uF and the bit higher voltage on the new one is good and V~ says it is an AC cap. As per the wire connections they can go any side. It will work just fine.

[tmcw]

Re: Motor Run/start up Capacitor - Replacement

Thanks for confirming that, I wasn't sure about the higher voltage, I know it's generally ok to go higher with caps on circuit boards, just wasn't sure about start-up caps.

I also wasn't sure about the metal mounting stub on the old one, versus the plastic stub on the new one, I was guessing it's more of a mechanical and cost thing, rather than an electrical thing.

[R_J]

Re: Motor Run/start up Capacitor - Replacement

The stud is just for mounting, and you are right, cost saving plastic so don't tighten it too hard.

[tmcw]

Re: Motor Run/start up Capacitor - Replacement

Thanks guys, motor up and running again with the new cap.

[Andrew F. Ali]

Re: Motor Run/start up Capacitor - Replacement

Great. Thanks for sharing.