Posted: 7/5/2017 8:23:12 PM EDT
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So I came home to the AC not working. Listened to it try to start and it sounded like the capacitor was bad. Took of the panel and found the cap no bulged but completely blown up. It looks like it arc'd on the cover and some of the debris in the find got scorched.
Is it normal for them to blowup rather than bulge? I can replace the cap but I don't want there to be something else wrong. |
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Usually it's smaller capacitors that will blow like that, the larger ones almost always have a relief cut/valve that will rupture to void the pressure. Do you know the rating on the capacitor?
Also if it blew like that there could be a direct short somewhere. How old is the AC? |
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I've direct shorted many capacitors in my day and none have blown like he is describing, it was either overcharged, or old and the dielectric in it has deteriorated. Quoted:
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There's a chance of a capacitor blowing up if you dead short it. Many years ago, when I was in technical school they told us to never direct short a capacitor because it might blow up. |
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I can replace the cap but I don't want there to be something else wrong. Replacement caps are cheap - which is why it's not a bad idea to keep a spare set on hand. Ditto for the power contactor relay. |
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Even capacitors that are supposed to have pressure relief built in blow up some times.
I've shorted lots of caps directly with a screwdriver and never had an issue. Having said that, a discharge resistor is smarter, espicially on big ones. The only one's I've blow up...I blew up on purpose by putting ~12V caps on 120VAC extension cords. 
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Wait a minute ... I've been told that you MUST short a capacitor to avoid getting a nasty shock. Screwdriver from C to Fan and then from C to Herm. So, do you short them or not? 27 years in the business, seen a lot of grenaded capacitors. It happens |