Friday, July 3, 2015

Replacing run capacitor in AC


AC unit contains circuits with up to 240V! Switch off power to the unit and use multimeter to confirm that the power is off before opening the cover.


Our air conditioning unit suddenly stopped working and started tripping breakers. While house fan would come on, condenser fan outside would not spin and breaker would trip immediately when thermostat would call for cool air.  After doing some research online one of the possible causes was suggested to be a run capacitor. Since we use AC very little and it worked for an hour or so before tripping the breakers, I figured that capacitor would be most likely source. The fan motor of the unit was spinning freely indicating that it is not seized. The contactor wold click when thermostat called for cold.

After making sure that breakers are off and there is no power to the unit, I opened cover of the electrical compartment. You can't mistake it for anything else as it has multiple warning labels printed on it. On my unit it is secured with 2 screws.
It is apparent that capacitor is busted as you can see that it is bulged upward in the picture below. For people who don't know, the capacitor is the large cylinder with the wires on top.

The Fix

Replacement capacitor can be ordered online for under $30 in most cases. If you want exact replacement it would be closer to $30. If you are OK using capacitor with the same characteristics but do not care about the exact size, it would cost less.
I picked capacitor from the TEMCo Industrial Power Supply. They are very reasonably priced on ebay - under $10 for dual run capacitor. They ship very fast and reply fast to your emails. Their capacitors have better characteristics than the original but they are much smaller in diameter - almost 1.5cm smaller. To secure the new capacitor I went to Home Depot and got some plumbers strips - galvanized metal strips with holes at a regular intervals. I picked a strip that has roughly the same thickness as the original bracket. Using pliers and drill, new bracket was made from the strip. It holds the new capacitor just as secure as the original bracket held the old capacitor. It took maybe 30 minutes to make the new bracket.
The new capacitor is connected by following markings on the old one. The markings are the same on the old and the new. One just needs to disconnect a wire and move it to the same terminal on the new capacitor.
After connecting and securing the new capacitor AC was powered up and it started without a hitch.
If you are still not sure if you want to do this yourself, there are tons of videos on youtube, which show the whole procedure from start to finish. If you are prudent and have some basic tools this repair is very easy and inexpensive. You will save 100s of dollars vs calling AC contractor to do the same thing.


Levi Eslinger said...

I fully agree with you that Youtube is a great source of information and help for doing almost anything! In your shoes, I'd be prepared to have a go at fixing an AC unit too because I'm very hands-on and practical. However, I understand how some would shy away and call in the professionals for an additional cost but peace of mind.

Dennis Cannon said...

Replacing the run capacitor is not too complicated. It may not be something that everyone wants to do on their own, though. I’d recommend any person who knows that has to be done but is reluctant to complete the task on his own to consult a professional. The replacement part is really affordable so the total cost of the fix should be low.

Dennis Cannon @ Laird And Son