# A/C run cap



## rakes9720 (Feb 10, 2005)

What causes a capacitor to fail? Would a short/problem in the compressor cause this? The unit would buzz loudly for a few seconds until the thermal protection switch in the compressor shut off. The hum of the fan motor would continue but it wouldn't run either (It's a duel cap). When the thermal switch reset, the compressor would buzz again and the electric meter would spin like crazy. (indicating a problem with the compressor?? Would a bad capacitor cause this??)

The capacitor is swollen at the ends and is obviously bad, but I am wondering if the broken cap is the problem, or a result of a different problem. Is it worth it to try a new cap, or will it fail too?

Thanks in advance,
Kyle


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## mdshunk (Mar 13, 2005)

That cap is probably your only problem, but make sure you also have 240 at the unit, and haven't lost a leg (only getting 120).


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## MechanicalDVR (Jun 23, 2007)

I haven't seen a single phase a/c compressor of any size yet that can start without a cap and if the cap body is puffed out, I'd say it's bad.


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## rakes9720 (Feb 10, 2005)

Hi. Sorry I forgot to respond. I changed the capacitor and it worked perfectly. I didn't expect the compressor to pull locked rotor amps because of a bad capacitor. Thanks for the help.


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## #CARRIERMAN (Jan 4, 2007)

Hi rakes9720

To help you understand why when the capacitor goes bad why a motor does not start properly. I won't go in depth into it but this is the shallow version. Think of a motor as a electromagnet, that being said. When you energize an electromagnet its job is to attract something to it. When you feed voltage to a motor it has two sets of electromagnets that are on the same phase. Rather its 120, 240 or what ever. The run capacitor causes an imbalance in the electromagnetic field allowing one to become stronger than the other. This is how the motor start itself, then the voltage between the two of them become mechanically imbalanced. I don't want to go any deeper into this subject for now, its almost a whole novel. But the easiest way to think of a run capacitor is like a sponge. Do not confuse a start capacitor with it though, they work two different way s. Using them improperly can get you hurt severely. Hope this help answer some of your question.

Good luck
Rusty


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