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Old 06-20-2021, 11:07 AM   #1
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A/C Capacitor Exploded

We have a Coleman Mach 15 air conditioner that stopped cooling, fan works and I could hear the compressor trying to start.

Removed the shroud and opened the capacitor box and found a 40 mfd 370VAC capacitor had come apart and spread it's guts all over.

I suspect this is the start capacitor for the compressor but I didn't do any more troubleshooting after finding the mess.

What do you think caused the capacitor to come apart and what else should I look for after replacing it?
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Old 06-20-2021, 11:12 AM   #2
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What do you think caused the capacitor to come apart and what else should I look for after replacing it?
Old age suicide !

One of mine did the same. Replaced it about 3 years ago, and all fine!
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Old 06-20-2021, 12:05 PM   #3
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Old-age suicide is well said and absolutely is most likely all that is wrong.

A HVAC tech would replace, measure amps with an amp meter to make sure all is in specs and button it back up. If your system has a start component (relay or solid state device) if a start component is shorted it can cause failure of the run capacitor, and the compressor will likely not run for more than a moment, even with a new capacitor. If start device is open it just won’t start as easily as it should especially when restarting quickly after shutting off. These problems are possible but not probable, typically.

Without that tool, just replace the capacitor, if the compressor runs, cools and doesn’t stop prematurely, doesn’t sound strange at startup, I’d put it back together and enjoy the cooling. If the outside and inside coils haven’t been cleaned recently, this would be a good time to check and clean if needed. But not to confuse things, dirty coils would not cause the capacitor to fail.
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Old 06-20-2021, 01:10 PM   #4
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If your system has a start component (relay or solid state device) if a start component is shorted it can cause failure of the run capacitor,
A run capacitor is designed to have voltage on them at all time. Now a start capacitor can only have voltage on them for a short time ( 10 seconds or less)or they will fail. Some times exploding and sound like a shotgun being shot.

To the OP.
What caused the run capacitor to go bad is a short within the capacitor itself.
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Old 06-20-2021, 02:07 PM   #5
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When ours went, I just went ahead and replaced all of them. They are not that much and figured they were about the same age.
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Old 06-20-2021, 06:08 PM   #6
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To the OP.
What caused the run capacitor to go bad is a short within the capacitor itself.[/QUOTE]

Well said. I might add for those of you that don't know capacitors, run capacitors are silver, start capacitors are black. You will always find a run capacitor but not always a start capacitor. It is up to the manufacturer if they install a start capacitor.
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Old 06-20-2021, 07:20 PM   #7
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start capacitors are black.
That use to be true but in the last several year I've seen a lot of imported things having a start capacitor being in a gray or blue plastic wrap. But I can say I've never seen a black plastic cased capacitor being anything other than a start capacitor.
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Old 06-20-2021, 07:50 PM   #8
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Originally Posted by Martind4 View Post
We have a Coleman Mach 15 air conditioner that stopped cooling, fan works and I could hear the compressor trying to start.

Removed the shroud and opened the capacitor box and found a 40 mfd 370VAC capacitor had come apart and spread it's guts all over.

I suspect this is the start capacitor for the compressor but I didn't do any more troubleshooting after finding the mess.

What do you think caused the capacitor to come apart and what else should I look for after replacing it?
A start capacitor is most always black plastic and is NOT oil filled and might not be factory It will also be accompanied with a potential relay. A run capacitor (which sounds like what you described) will be silver metal and oil filled (the oil cools and insulates) A 40"sounds " big but maybe not. Over the last 10 years most manufacturers are using Chinese made capacitors AND THERE FOR CRAP many of the others are no better. Try finding a Mexican made Cap and get a spare. As compressors have gone up in efficiency. the capacitors have gone down in reliability. A typical 3 ton Heat pump cap in Florida won't last more that 3-4 years these days. Do use a clamp on AMP meter and make sure once running again it is near or below Full load running amperage as shown on the unit name plate.
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Old 06-21-2021, 06:20 AM   #9
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I just replaced all the capacitors in one of my heat pumps. The start capacitor had come apart so I just replaced them all. Started right up and is working fine. Change them all while it is open. JMHO
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Old 06-21-2021, 02:20 PM   #10
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I cant speak for your RV AC, but I believe a home AC that has a Start Capacitor is controlled by a Potential Relay which allows the start cap to remain in the circuit ONLY for the brief start up time then it drops out but if that fails and its left in it can explode...

John T BSEE,JD NOT an RV AC or HVAC expert so NO warranty this may be wrong as rain ...........
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Old 06-21-2021, 04:19 PM   #11
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Quote:
Originally Posted by Martind4 View Post
We have a Coleman Mach 15 air conditioner that stopped cooling, fan works and I could hear the compressor trying to start.

Removed the shroud and opened the capacitor box and found a 40 mfd 370VAC capacitor had come apart and spread it's guts all over.

I suspect this is the start capacitor for the compressor but I didn't do any more troubleshooting after finding the mess.

What do you think caused the capacitor to come apart and what else should I look for after replacing it?
Aside from the normal wear and failing that all the others have talked about, a low voltage situation will also cause the start capacitors to fail.

I have a Colman Mach 6535 basement AC with 2 compressors, hence 2 start and 2 run capacitors. I woke up one night this spring while running the heat pump hearing it keep starting and stopping, or trying to.

Short version of the story, after much diagnosis, the 50 amp breaker in the CG pedestal was wonky. Tested at 120/120 and 240. But put even a 3 amp load from the charger on it and the voltage dropped to 37. Spent a lot of time exploring and diagnosing after the electrician was out and said the pedestal was fine. I swapped out the 50 amp breaker called him a liar, and now all is well, other than the $860 for 4 capacitors a relay a control board and a good Winnebago tech who knew how to replace the old with the new upgraded board.
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Old 06-21-2021, 05:56 PM   #12
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I can't speak for the first 10 ears of it's life, but for the last 5 years I don't think it's been exposed to a low voltage situation. The Progressive Industries EMS has been keeping an eye on things.

Thanks for all the input. I'll let you know if the new capacitors fix the problem. They've been ordered and my son-in-law will install next weekend, my wife won't let me up in the roof anymore.
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Old 06-22-2021, 05:41 AM   #13
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Originally Posted by Martind4 View Post
I can't speak for the first 10 ears of it's life, but for the last 5 years I don't think it's been exposed to a low voltage situation. The Progressive Industries EMS has been keeping an eye on things.

Thanks for all the input. I'll let you know if the new capacitors fix the problem. They've been ordered and my son-in-law will install next weekend, my wife won't let me up in the roof anymore.

Tell the son in law to double check that the connections on the capacitors are tight when he replaces them. I had a not tight enough connection once and had to tear things apart a second time. Things worked fine after that.
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Old 06-22-2021, 07:31 PM   #14
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I cant speak for your RV AC, but I believe a home AC that has a Start Capacitor is controlled by a Potential Relay which allows the start cap to remain in the circuit ONLY for the brief start up time then it drops out but if that fails and its left in it can explode...

John T BSEE,JD NOT an RV AC or HVAC expert so NO warranty this may be wrong as rain ...........
You are correct. For years MH a/c's used potential relays. Failures were very common as potential relays work off of pick up voltage off the run windings. For example, pick up voltage could be say 165v. When you were in a campground with say 102 volts, the relay would stay in start relay mode, as the pickup voltage would not be enough to keep capacitor out of the circuit during operation. Nowadays almost all are using solid state replays that are not voltage sensitive
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