Air Conditioner Repair
It is also possible that you have a seperate starting winding (with or without capicitor - much smaller capacitor if capacitor is used), and the cut-out switch (one the compressor is up to speed) is defective, not disconnecting the start winding. If this is what you have, you can test this by disconnecting the start winding once the compressor is going, and see if the run current drops down to normal.
Answer:
I took the AC apart and traced the wires. The 15 MFD side of the capacitor went to one side of the compressor and the 3 MFD side of the cap went to one side of the fan motor. The common wire of both the fan and compressor motor went to the center terminal of the cap. I found someone with a capacitor tester and the cap tested OK. Someone else also brought me another double cap from a larger old AC unit rated 10/25 MFD and this also checked OK on the tester. By the way, it had a fourth "terminal" which was grounded to the case. My 3/15 cap was grounded by a steel clamp around the cap body if it made contact at all through the paint on the case. In any case I first put the old cap back in after cleaning everything I could just to see if dirt was a problem and to make sure everything was hooked up properly. Same problem, not that I was surprised. Would run and cool for about 1.5 minutes with a laboring sound and drawing 14-15 amps. I put a second meter across the cap terminals and it read 120 VAC. I next substituted first the 25 MFD side of the other cap for the 15, same problem and the motor sounded even more labored till it cut out, and then I tried with the 10 MFD side, same problem. By now the hermetic compressor can felt warm and it would cut out sooner probably because it was still warm from the previous trial. I never changed the cap on the fan motor side because it ran fine and I didn't want to screw anything up that was working. After reading 4 books on AC repair and running through these exercises, it seems that both the fan and compres- sor use run capacitors and neither use a start capacitor with cutout switch. The only other possibility is if the start cap is in the metal housing that covers the terminals where the 3 wires go into the compressor can, but it would have to be small or in the can itself which is inaccessible. By the way I measured resistance of the two coils of the compressor motor. The coil in series with the 15 MFD cap was 11 ohms, and the run coil was 1 ohm. The coils in the fan motor were higher, but that only draws 0.5 amp either on low or high speed. Sounds like the compressor is Kaput and the AC is ready for the scrap heap. I already have a taker for the caps and fan motor. I hope this summary helps anyone else trying to fix their AC unit.