What can make a capacitor explode?

Hey guys, I have a problem with one of the AC units in a house I just bought. It’s a Whirlpool ACM184XJ1. I finally had a few minutes to mess with it to try to make it work, and the first problem I ran into is that the circuit breaker was blown. I reset the breaker and and turned on just the fan. The fan ran for about 30 seconds, then the unit made a loud “POP” along with a bit of smoke and then the fan shut off, then a small amount of black oil started running out from behind the control panel, presumably where the capacitor is, although I’m not certain since I just bought this house and I’ve never had this unit apart. I think there is a wiring problem, but I didn’t look yet since I had no way to take that 18K BTU beast out of the wall myself, especially since I have a bad back. I am going to get one of my buddies to help me get the unit out of the wall so I can work on it. So my question is presuming I don’t see anything obviously wrong with the wiring when I get the unit out of the wall, was the capacitor likely just defective, or is there something else that caused the capacitor to explode, like a short? Thank you in advance for taking the time to try to help.

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Capacitors fail.

They might fail for a multitude of reasons but when they fail catastrophically they tend to go pop and spew oily, waxy grease from the casing so what has happend is not unusual, what caused it though?? with out looking that is anyone's guess.

I'd guess the capacitor failed and took the breaker out. You reset breaker and capacitor resumed failed state once it had heated up and then tripped the breaker. Chances are it is just the capacitor that has given up but to make sure a full electrical test on the motor winding's and supplies to prove the electrics are good.

Capacitors are cheap enough and relatively easily sourced so it should be easy to prove one way or the other.

Regards
Rob

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The main reason is low quality and cheap materials in the production of the capacitors.

I still see 40 and more years old capacitors on Copeland condensing units.

Thanks for your help. When I have the time to get the A.C. out of the wall so I can work on it, I’ll report back with what I find. But my concern is if I can’t find anything wrong with the unit besides the capacitor and I just replace the cap and go on with life, there could still be a problem with the unit that could be a safety hazard. Is that a logical concern? Thanks.

Yes it is! Beter to call electrician to check running curents and voltages are within specificaction.