airxcel rooftop ac unit capacitor test

Thanks everyone

It is not that easy to test a start capacitor, because most of them have bleeder resistors on them. That said- on most new models *if* they have a start capacitor, and the start circuit has failed, it will be the PTCR device which has burned up. If the start cap itself is bad, they will usually show physical signs of failure.

Identify ,mark, remove wires from cap. Use a digital meter on the 10k scale. Put one lead on one terminal and tap the other lead on the other terminal. Should get a deflection up the scale. If no deflection the cap is defective. Watch out cause cap is now charged, Discharge across terminals with a screwdriver. Grainger has the caps for sale. Better yet order a Spp6 Supco hard start cap/relay off ebay. Remove old start cap/wiring and install new component.

Best test is to swap it out and see if it fixes the problem. They're cheap, can't hurt to have an extra on hand anyhow. There are testers for them, but they don't test at the voltages and currents these are running at so they'll tell you if it's really catastrophically bad, but don't guarantee it's good if it tests OK.

As to where to get them - any air conditioning shop will have a variety, as will many electrical suppliers, some old fashioned hardware stores, and places like Granger Supply.

Best is to take it out and with you to the supplier and have them match it up spec for spec. They usually have wires that plug on to the terminals. Make sure you mark the wires, or take a picture, so you can put it back the way it was.

CAUTION: Make sure the power is off to the unit, flip off the breaker, etc. AND short across the leads with a screwdriver or knife or similar to ensure it has been discharged. They can hold a nasty charge for quite some time.

It's really easier than it seems to swap one out, usually takes more time to get to it than to swap it out.