Motor on air compressor

[NormL]

It was the starting capacitor. The guy at rebuild shop didn't have the right one to replace it, but he had one that was a different form factor so he connected it and tested the motor, it ran fine and starting torque was good. Charged me $20 for diagnostics. Then it gets interesting. Went to an online site that sells replacement parts for Sanborn compressors, they want $130 for the starting capacitor, that sounds nuts. So I go online at Graingers and they sell an equivalent one for $13.50, so I ordered it. Mission accomplished. thanks for help and suggestions.

I had the same scenario last year in spring with mine. The previous fall it was still starting up, although it seemed sluggish. In spring it just sat and hummed. Advertized for a replacement and the only response I got was from someone who had a motor but advised me to bring mine down because it is rare for a compressor motor to be "smoked" (burned out). He was right, of coarse, and with a new capacitor it works like new!

Where my story differs from yours is that when I bought the compressor it was as is, not running. The cut-in cut-out switch contacts had welded themselves together before the breaker tripped. Maybe the shop personnel kept resetting the breaker till the compressor just quit, I don't know. I didn't ask. With the cost of the repairs I made to it, I have a compressor that cost me 1/3 the price of a new one.

 

[Stimw]

I got a Coleman 2hp compressor that I found on trash day. A $6.69 capacitor from Grainger and it runs like new!
My true 5hp (175psi) shop compressor will burn out the start capacitor about every 10 years.

Pump motors use start switches and capacitors. A lot of start switches you can clean the contacts and get them going again.