Air compressor question!!

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11-07-2011, 01:57 PM
miataspeedracer

Air compressor question!!

Here's the deal. Inherited an older Sanborn Black Max 3HP portable air compressor from my stepfather. Prior to me picking it up 2 weeks ago, it worked like a charm. Last run about 2 months ago without issues. So I haul this thing home, clean it up a bit, drain the tank, and try to start it up. Motor hums for about 2 seconds, then shuts down. Realized after the third failed attempt that it's tripping the circuit breaker (20 amp) in the garage. Let it sit. This past weekend, I tried plugging it into the outlet that runs our washer (twin 30 amp fuses). Motor hums for about 6 seconds, then trips the breaker on that, too. (I checked with my step-dad--the compressor was plugged into their garage outlet on a 20 amp fuse.)
So...something ain't right. The belt is NOT binding, so that's not the issue. I don't see any loose wires. I did spray it down with a bit of Simple Green and did a light rinse when I got it. Could THAT have caused the issue?

Any thoughts on what the issue could be? Anyone know anyone local (Plano-area) that does compressor diagnostics/repair?
11-07-2011, 02:00 PM
Rob®

Someone knick a wire while moving it, causing it to short out?
11-07-2011, 02:08 PM
miataspeedracer

Quote:

Originally Posted by Rob®

Someone knick a wire while moving it, causing it to short out?

Not that I can see.
11-07-2011, 02:41 PM
HudsonHawk

Motor may be sstuck from non-use. tap it with a hammer or wrench.
11-07-2011, 02:55 PM
POS Racing

Start capacitor on the motor may have gone to a better place.

With the unit unplugged can you turn over the compressor by hand??
11-07-2011, 03:48 PM
miataspeedracer

Quote:

Originally Posted by POS Racing

Start capacitor on the motor may have gone to a better place.

With the unit unplugged can you turn over the compressor by hand??

If you"re asking if I can turn the belt, the answer is yes.
11-07-2011, 04:23 PM
Titus

But is the belt turning the compressor wheel, or is it slipping?
11-07-2011, 04:27 PM
miataspeedracer

Quote:

Originally Posted by Titus

But is the belt turning the compressor wheel, or is it slipping?

When Gary came over to check it out, we looked at the belt to see if everything was turning properly. No issues there. I'm certainly no expert, but I'm getting the sense this is an electrical issue instead of a mechanical one.
11-07-2011, 04:27 PM
miataspeedracer

Quote:

Originally Posted by Titus

But is the belt turning the compressor wheel, or is it slipping?

When Gary came over to check it out, we looked at the belt to see if everything was turning properly. No issues there. I'm certainly no expert, but I'm getting the sense this is an electrical issue instead of a mechanical one.
11-07-2011, 04:44 PM
onething

Starting capacitor.
11-07-2011, 04:52 PM
patf

+1 on capacitor its the little lump on the electric motor
11-07-2011, 05:07 PM
miataspeedracer

Ok, I'll start with the capacitor. I assume start capacitors are generic and not brand-specific. Is this something a Home Depot/Elliott's would carry?
There are two lumps on the electric motor. One contains a black "can" that is wired with purple and green wires. The other is a sliver "can" that is wired with black and red wires. Which one am I looking for?
11-07-2011, 05:12 PM
tailchaser

Are the starter caps not helpful like the ones on AC condensors? Mine always bulge out so it's obvious they've died...

Grainger has them in ac condensor sizes... not sure where to go for compressors.
11-07-2011, 05:13 PM
sammm

^Be careful when messing with capacitors! Even if your compressor is unplugged, they can (and will) knock you on your arse!

I'd google the motor model for an owner's manual or specific info. regarding which one you want.
11-07-2011, 06:36 PM
SirHustlerEsq

I thin you'll need a trip to Fry's. Get the multimeter out and go to town.

Unplug the compressor and attempt to start it to clear the caps.
11-07-2011, 07:16 PM
onething

With the compressor unplugged, take a screwdriver and short the connecting points of each capacitor.
11-07-2011, 10:08 PM
tailchaser

Quote:

Originally Posted by onething

With the compressor unplugged, take a screwdriver and short the connecting points of each capacitor.

This is a good idea only with relatively small caps...
11-08-2011, 07:10 PM
SirHustlerEsq

Quote:

Originally Posted by tailchaser

This is a good idea only with relatively small caps...

...caps small enough to not stop your heart.
11-10-2011, 08:40 PM
Mr. Miatie

Single phase, three phase..? Id put a buck on the starter too.
11-24-2011, 10:43 AM
miataspeedracer

Update: took the start capacitor and the run capacitor to have them checked out. No issues with the start capacitor, but the run capacitor was shot. Bought a new one and brought it home. Problem solved? No! Plugged it into the wall, failed start and blown fuse 2 seconds later.
Thoughts? Could the motor itself have gone bad?