# change capacitor on outside AC unit



## rockyroller (27 May 2022)

anyone ever change the capacitor on their outside AC unit?

2nd week w/ an A/C tech no-show. I've google-diagnosed the problem. certainly couldn't hurt it by replacing this part, even if that doesn't resolve the issue. seems super simple


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## Cycleops (27 May 2022)

I gotta tell you RR that it never gets that hot in the U.K. Never had the need to change the capacitor on ours here, only re-gas it.


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## irw (28 May 2022)

rockyroller said:


> anyone ever change the capacitor on their outside AC unit?
> 
> 2nd week w/ an A/C tech no-show. I've google-diagnosed the problem. certainly couldn't hurt it by replacing this part, even if that doesn't resolve the issue. seems super simple



Hmm. Capacitors you say…Apologies if you are aware of the dangers already, but if you don’t, please be aware that capacitors can be very dangerous, even if the equipment hasn’t been turned on in a while.


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## Tenkaykev (28 May 2022)

Is the capacitor for the compressor? The “ start” capacitor is electrolytic and usually of a high value in the region of 80-250 mfd. “ permanent “ or run capacitors are usually of lower value. Some will have a discharge resistor wired across the terminals, but its good practice to short the terminals with an insulated screwdriver. I changed many hundreds over the years when I repaired Electric motors.


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## gbb (28 May 2022)

Changed them at work several times on AC motors, I'm just careful not to touch the terminals together, never had an issue. If a motor is a non starter, its the cheapest, easiest, most obvious place to start.


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## rockyroller (28 May 2022)

thanks guys I may give them 1 more week, call another company & if still on my own, research the correct part & pricing


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## ColinJ (28 May 2022)

irw said:


> Hmm. Capacitors you say…Apologies if you are aware of the dangers already, but if you don’t, please be aware that capacitors can be very dangerous, even if the equipment hasn’t been turned on in a while.




Yikes - I wasn't expecting _*THAT*_! 

Yes, I'm positive that RED = positive...


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## Tenkaykev (28 May 2022)

rockyroller said:


> thanks guys I may give them 1 more week, call another company & if still on my own, research the correct part & pricing



The value and voltage is often printed on the capacitor.


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## ColinJ (28 May 2022)

Tenkaykev said:


> The value and voltage is often printed on the capacitor.



Which can be found decorating the ceiling if you do what the guy in the video did!


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## Andy_R (28 May 2022)

ColinJ said:


> Which can be found decorating the ceiling if you do what the guy in the video did!



The guy in the video is actually a very experienced and qualified electrical engineer. He has a lot of videos on You tube where things always go spectacularly wrong, but he never gets injured - strange that isn't it...Look up "ElectroBoom"


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## presta (28 May 2022)

irw said:


> capacitors can be very dangerous, even if the equipment hasn’t been turned on in a while.


Most who work with electronics have had small electrolytics go pop every once in a while, but the ones that are big enough to be dangerous have safety vents, so they don't do anything worse than squirt a load of mess out of the relief valve rather than exploding. I've seen that guy in that video before, he comes across as someone who's putting on an inept act for 'comic' effect.

If it's a high voltage circuit, the bigger risk with capacitors is a charge remaining after switch off, not only should you ensure they're discharged before handling, but some are unaware that _they need to remain shorted_. If you discharge a capacitor then remove the short, they can partially _recharge _themselves because the electrical stress remains within the dielectric for some time. The main isolator switches on our big transmitters had contacts that shorted the main HT supply, and kept it shorted all the time the power was off.


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## the_mikey (29 May 2022)

rockyroller said:


> anyone ever change the capacitor on their outside AC unit?
> 
> 2nd week w/ an A/C tech no-show. I've google-diagnosed the problem. certainly couldn't hurt it by replacing this part, even if that doesn't resolve the issue. seems super simple



When you say "the capacitor" it makes me think it's simply a capacitor for getting a brushless motor running and not a power supply or control board issue, do it if you think there's power getting to the motor but it's failing to turn somehow.


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## Tenkaykev (29 May 2022)

presta said:


> Most who work with electronics have had small electrolytics go pop every once in a while, but the ones that are big enough to be dangerous have safety vents, so they don't do anything worse than squirt a load of mess out of the relief valve rather than exploding. I've seen that guy in that video before, he comes across as someone who's putting on an inept act for 'comic' effect.
> 
> If it's a high voltage circuit, the bigger risk with capacitors is a charge remaining after switch off, not only should you ensure they're discharged before handling, but some are unaware that _they need to remain shorted_. If you discharge a capacitor then remove the short, they can partially _recharge _themselves because the electrical stress remains within the dielectric for some time. The main isolator switches on our big transmitters had contacts that shorted the main HT supply, and kept it shorted all the time the power was off.


Yes, that caught me out once, a cap I’d discharged earlier gave me a belt when I was refitting it later. It became second nature to touch the terminals to my bench vice after that incident.


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