Need Air Compressor Help

[39deluxe]

Went out to do some sanding and grinding and kicked on the compressor. It ran fine and pumped up and shut off. I was just getting into tight corners with my small air grinder and not using much air. Then the next time it started it just made a loud hum and kicked off the circuit breaker before I could get to the switch. The flywheel turned a little before it hummed and quit.

It turns freely by hand and I just put on a new switch a few weeks ago because the old one was leaking air. It's been running just fine for 10 years and never had a problem except for 2 switch replacements.

It's a Sanborn 60 gal. vertical 5 hp magnetic start that cycles between 145 and 175 psi.


The switch clicks on and off but nothing else happens. Not humming or anything. Any ideas?

Tom

[kb426]

Check to see if voltage is making it through the switch. If that's ok, I'd look for a bad capacitor or motor. That hum concerns me.

[39deluxe]

I'll check that switch in the morning. I got it off Ebay but I did step up to a higher amp rating. The old one was a $12.00 Ebay 18 amp and it lasted about 10 years. I had to replace the original switch when I got the compressor from my father in law. It was bad when he bought it new and wouldn't turn off. He'd just let the safety lift then kill the breaker.


Today I just switched to my backup unit which is a 30 gallon Sears stationary I bought back in the late '70s. I have a lot of hours on that one painting and running air tools and it's never failed me.


Thanks,
Tom

[39deluxe]

Well, that was interesting. I didn't have any continuity across the left side of the switch. I could see the contacts closing on the right side but had to disconnect the air tube and turn the switch to see the left side. The left side contact wasn't even moving and appeared to be bent. I stuck my screwdriver in there and pushed up on the middle of the contact arm bending it some and then it started closing again. Turned on the breaker and cycled it several times and it seems to be working for now.

We'll see how long it lasts.

Tom