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Bobcat79
Premium Member
join:2001-02-04

Bobcat79 to Dogwood

Premium Member

to Dogwood

Re: A/C Compressor/Fan Run Capacitor

How do you guys know the capacitor failed? Don't they normally get weak and start leaking (electrically), instead of a catastrophic failure?

I had all three capacitors in my condenser unit replaced a few years ago. But I'm just wondering how you're diagnosing the problem.

John97
Over The Hills And Far Away
Premium Member
join:2000-11-14
Spring Hill, FL

John97

Premium Member

In my previous life, I used to work on pump systems that had starting capacitors that would drop like flies once we started getting hot days. So, I've seen my fair share of blown capacitors.

When my compressor wouldn't kick on, I checked the capacitor in my unit and the bottom was bulged out instead of being flat. This is a telltale sign of a blown capacitor.

Sometimes they will also leak (oil) when they are blown, and you can always test them with a meter.

ArgMeMatey
join:2001-08-09
Milwaukee, WI

ArgMeMatey to Bobcat79

Member

to Bobcat79
said by Bobcat79:

How do you guys know the capacitor failed? Don't they normally get weak and start leaking (electrically), instead of a catastrophic failure?

I had all three capacitors in my condenser unit replaced a few years ago. But I'm just wondering how you're diagnosing the problem.
I've referred to this as a popped hat, and I am pretty sure I heard that from somebody else. Somewhat related Wiki article ... »en.wikipedia.org/wiki/Ca ··· r_plague

Dogwood
Premium Member
join:2001-01-14
Texas

1 edit

Dogwood to Bobcat79

Premium Member

to Bobcat79
said by Bobcat79:

How do you guys know the capacitor failed? Don't they normally get weak and start leaking (electrically), instead of a catastrophic failure?

First clue was the Cap was passing the 120VAC to the motors, but nothing was happening, just a very quiet hum from the compressor.
As I was removing the cap I noticed that the aluminum housing was bulged at the top and bottom, this is from overpressure during the internal short circuit.
The blowout port was not breached.
I checked it with a capacitance meter and there was none, a direct short from the common terminal to the compressor terminal as well as from the com to fan terminals.
You could check the cap with a capacitance meter as your regular PM, it wouldn't hurt.
Replacing the run caps on a regular basis seems like a good idea now, and I'm ordering a spare this week, also install a start cap kit is good and should lengthen the run cap's life.
Bobcat79
Premium Member
join:2001-02-04

Bobcat79

Premium Member

My symptoms were that the compressor would not start the first time in the morning. Once it got started, it was good to go for the rest of the day. Replacing the caps solved the problem.

I used to work for a company that made electronic equipment. We had a guy who did testing, and was very good at hearing the sizzle from a cap that was installed backwards. He had the timing down perfect. When that happened, he would call someone over and ask if they smelled anything burning. Just as the person started sniffing around the equipment - POP! - the end of the cap would blow off.

zen1
@optonline.net

zen1 to John97

Anon

to John97
said by John97:

In my previous life, I used to work on pump systems that had starting capacitors that would drop like flies once we started getting hot days. So, I've seen my fair share of blown capacitors.

When my compressor wouldn't kick on, I checked the capacitor in my unit and the bottom was bulged out instead of being flat. This is a telltale sign of a blown capacitor.

Sometimes they will also leak (oil) when they are blown, and you can always test them with a meter.

that failure is due to the current the caps have to endure, hot days makes it worse because the caps get even hotter, the fix for that is to parallel 2 caps of half the capacitance, this way, each cap only has to pass half the current.. you get the same capacitance as using 1 cap btw.