Compressor on the fritz.

[imagineer]

My air compressor stopped running this past weekend. No warning signs or weird noises. It cycled normally until the pressure switch cut off, then next time it should have started, it didn't.

It's getting power through the pressure switch to the motor. The pump spins easily, so I know it's not locked up. Neither the start or run capacitors are visibly popped or swelled.

Any way to check the motor (without disassembly)?



I've got both capacitors here with me and will test them using the maintenance shop's multimeter.

 

[gamescastspencer]

Is there a Klixon switch (red button) on the motor? Is it tripped?

 

[imagineer]

Yes, there's a red button. I pressed it and it didn't help. Quick update, both the start and run capacitors are good.

Looks like the motor is shot. I shouldn't complain though...I bought this compressor (Husky, 60gal, 2 stage) over 20 years ago and it was well used then.

The label on the storage tank states it can produce 7.5hp Peak. The motor plate doesn't call out a horsepower rating, but it states it pulls 15 amps (@ 220V). Checking available continuous duty motors, some of the 5hp options also show to pull 15 amps. Think that's a suitable replacement?

 

[gamescastspencer]

The 7.5hp figure is like shop vac horse power, rather dreamy.

I see on the tag is says 2.98kw output, which converts to just shy of 4hp.

You could go up to a 5hp motor if your electrical supports it, or down to a 3hp if you were to adjust the drive pulley, that will result in a loss of CFM, slowing the pump down.

 

[micromind]

How hard did you press the red button?

It takes a very hard, almost thumb busting hard press to reset a Klixon.

 

[OccupantRJ]

Have you checked the wiring connections inside the motor junction box on the motor, or just at the output from the pressure switch? I have seen several motors over the years where a connection in the motor junction box (peckerhead) failed, likely due to vibration.

 

[imagineer]

How hard did you press the red button?

It takes a very hard, almost thumb busting hard press to reset a Klixon.

Thanks Micromind, for the tip on the red button. I'll give it another, more deliberate, shot this evening.

OccupantRJ, I checked for voltage at the output side of the pressure switch but will eyeball the connectors inside the motor junction box.

 

[The Cobbler]

is there a centrifugal start switch? mine ( compressor) did the same as yours & the contacts were dirty.

posted here

 

[imagineer]

No go on the little red button. I pressed with everything I could muster and it didn't budge. I even used a bar clamp on it and turned on the power while the clamp was squeezing the button, and nothing.

Given that this compressor is at least 25 years old and has lived a rough life (in a woodworking shop prior to me housing it in an uninsulated pole barn since 2003), I've ordered a replacement motor. Down the road, if I'm lacking something to do, I'll open up this motor and see if I can diagnose what went wrong.

 

[Milton Shaw]

I had one 5hp compressor that burned out one motor and bought another motor for it. Within a month or so it started tripping out on overload on motor. The whole works was 35 years old and so I tried the motor without a load ( took belt off) the motor would run without overheating and because of age of compressor and tank, I just replaced them with a deal I got at Northern too. I bought a customer return with $600 off with a full warranty. They had no where to test it so I took it as returned. Sure enough the motor was bad and I had to wait a full 4 days for someone to come from 250 miles away to put a new motor on it. It's been 3 years no other problems just the sweet taste of $600 off deal.