How can i check a dual capacitor on ac unit to see if its bad?
Question:lennox brand ac, 35/5 mfd -370 round
Answers:
Most accurate way is with a microfarad tester. It provides power to the cap and reads the capacity for storing energy.
Quick way is to shut the power to the unit, jump the leads on the pins and repower the unit. If the motor &/or compressor start on demand, the cap is bad. It is possible that one side of the dual cap will go out, and the other side is still serviceable. If you can't find a dual cap, you can get a 35 and a 5 and bridge the common terminals with a jump lead.
well the quickest answer is if the head of it is buldged out or any waxy/tar like fluid leaking out of it. The top of the run cap should be flat like the top of a can in your cubbard, some times its VERRY obvious some time very subtle. Another quick method is tell the a/c to come on, if the fan is not running, use a screw driver and spin the fan blades, if it spins up then its a bad run cap, and you probably heard the compressor give a quick "buzz" noise for a sec before stoping. Dual run caps are a common and cheap replacement and dont cause any lasting damage when they fail. Another quick way if you do not have a volt meter that can check runcaps(Fluke has several that do) take the wires off the cap PAYING ATTENSION WHAT GOES WHERE. take a meter and set it to Ohms, or resistance. Put the probes across the "C" and "HERM" terminals. The should start showing an increase in resistance before showing showing "OL" on the display. If it shows "OL" as soon as the probes are placed on the terminals or never you see a series of numbers without climbing to the "OL" then the cap is bad. good luck or call a company to come out, That part usually retails for about $20-30 though it you can find one its about $7-10 cost.
I can only assume that you don't have a microfarad tester...take it to a hvac supply store and ask if they have a replacement cause you think it may be bad, they will pull out a meter, check it for you and tell you whether or not it is bad and since you're already there, you can get a new one. I just did this a month ago and completely forgot that my meter had a mf selector on it, I wasn't using my head.
Licensed Electrical Contractor
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