Blown capacitor leading to other problems?


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Old 08-06-15, 09:17 AM
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Blown capacitor leading to other problems?

Hey everyone, totally new to these forums(I'd assume this happens a lot as non-handy people like me have their stuff break...).

Anyways, yesterday my wife noticed the AC running but the house was quite hot. I identified this to be a capacitor issue because I was able to spin the blade and get it to fire up. The only problem is that it is still blowing warm air and I think the air flow is lower than before by a lot, but I never really put my hand close to the vents prior so I can't be certain.

I have read other things about freezing being a problem or I didn't know if a unit trying to run while the outside unit wasn't spinning could mess up something else. I do think the AC probably ran for a couple hours without the outside unit working, but then we had it off the rest of the night to avoid causing any sort of damage.

Every other instance I read online where somebody is discovering a blown capacitor on the outside unit, it seems like the replacement of that is fixing the problem. I still haven't replaced mine, but if I can manually fire it on and it still blows warm air, what else might be going on? Any tips or advice I'd be so grateful to receive.
 
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Old 08-06-15, 09:47 AM
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Adam, if the evaporator coil (inside the house) freezes up, it will significantly reduce the airflow through the vents. However, for the evaporator to freeze up, the outside unit would have to be working properly and have restricted airflow inside (due to dirty filter or evaporator coil).

In your case, it appears that the outside unit isn't working, so you shouldn't have a frozen evaporator coil. In all likelihood, the capacitor for the condenser fan is bad, which is why it isn't starting up without a push. The condenser fan also cools the compressor. Without the fan running, the compressor will overheat and the thermal cutout will turn on, shutting down the compressor so that the compressor isn't damaged. It could take several hours for the compressor to cool sufficiently for it to start working again.

I would suggest the following course of action. Replace the capacitor in the outdoor unit. Turn off the power to the unit and short out the capacitor terminals with a screwdriver after turning off the power. You probably will find a dual capacitor (two capacitors in a single "can"). If so, it will have 3 terminals. Replace it with a new cap with the same mfd values. The voltage rating can be the same or higher. If you have two separate capacitors, the one with the smaller value (typically ~5mfd) will be the fan capacitor.
 
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Old 08-06-15, 09:57 AM
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Thanks a ton Bob! I am actually super certain it is a bad dual cap outside and am in the process of searching one out in town. But if I go manually fire off that fan with a stick, even with a bad capacitor, would I expect cold air - given I kept everything turned off for maybe 10 hours?
 
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Old 08-06-15, 10:25 AM
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Yes, you should be able to test the unit by manually starting the condenser fan. However, I wouldn't let it run too long that way, as sometimes the fan doesn't run at full speed, and if it doesn't, the compressor may overheat again. I would run it 5-10 minutes, long enough to verify that you're getting cool air, and then shut it down.
 
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Old 08-13-15, 08:01 AM
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I never made it back here last week, but wanted to provide an update. Well, it turns out the capacitor was all that was wrong. I wanted to thank you Bob for walking me through the fix and troubleshooting. Really helpful site and people!
 
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Old 08-13-15, 09:07 AM
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Adam, thanks for letting us know the outcome. Glad to hear that you got it fixed and that we could help.
 
 

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