I tried to run the air conditioner today, its warmed up and don't need heat anymore, now I have no cold air either, but everything is on except possibly the compressor. I stood outside to listen and there is a short buzz about every 15 to 20 seconds, I suppose the compressor trying to kick in but won't.. What parts do I need to fix this or is it a freon problem. I just had it filled and serviced last year at this time, freon and some kind of points were put in. The lines are both the same temp too. No change of temp I can detect on the coils on the inside unit either. Last year I called for service because the inside was freezing over but is not this year. I don't think the compressor is kicking in. What do you suggest. Checked the capacitor with my multi meter and it shows there is conductivity, is it worth trying to use a hard start, because its probably ran its life by now being 13 yrs old

I would be leaning toward a compressor start issue. If you are hearing it try and start up but just can't muster the kick then I would try a hard start kit. Don't know how DIY interested you are in doing it but just speaking for myself I like the 5-2-1 compressor savers. Super easy to hook up. They keep going on and on.

I would ohm out the compressor terminals since you know how to use your meter and make sure you still have continuity between C-R and C- S R-S. If you do just double check wires that may be frayed or a terminal burned off even at the compressor hook ups. If all that checks I would be looking at a hard start. Anyone else?

Not to plug videos too much but at minute :48 you will see one here on a 3 ton heat pump.

visual tour of an outdoor unit - thermal-medics FREE online HVAC repair and consumer advocate

Once again, thermal, great video.

Ricky, I think thermals on the right track here, but I would also suggest checking the compressor run capacitor first and foremost. If the run cap is bad or weak
, it may cause the compressor to hum but not start. It will do this over and over again causing the compressor internal overload to trip in about the time frame you suggested. If the run cap is good, a hard start kit is your next best bet. However, if the run cap is bad, a hard start kit will not completely solve your problem. A hard start is just that. It gives an extra shot of "power" to help start the compressor. A run capacitor both gives a boost and actually aids in the correct running of the compressor or motor. While a start cap drops out after initial starting of motor, a run cap is still always having power pass through it, and helps the motor run better. Without the run capacitor, the motor will draw high amps and will eventually cause the internal overload to trip. So, a hard start kit is always a good Idea, even on new units (just helps the compressor start up easier) but will not replace a run capacitor, which is designed to help the motor start and run.

One more thing. Take it as a good sign that your compressor is at least humming. This usually means that the windings are good. Just not getting enough boost to start. So, as mentioned above, it is most likely a bad run cap, or in need of a hard start kit. Please do let us know what you find.

Man, thanks for that. Good catch.

I saw 'checked run capacitor' but didn't sink in about the ohmmeter. He is right on about the run cap first. The only way I know to check the run cap accurately with an ohmmeter is to use an analog one. Otherwise you got to have a mfd rating on the multimeter.