I was gonna blow out the shop this morning, and my compressor stopped working.

It kicked on, ran for about 1 second, and then stopped. The motor was buzzing like it was locked up. I was right next to it when it happen so I immediately turned it off.

I figured either the motor or pump was locked up. I took the belt cover off and both the motor and pump turn easily.

There are two capacitors on top of the motor. Could one of those be the problem?

BTW it's 5hp, 60 gallon, upright 220v, dual cylinder pump

It sure could. There is a start cap and a run cap, just replace them both, pretty simple. You will need to either go to Grainger or a motor shop to get them. They have to be the correct MFd (micro fared) and size to go back inside the covers.

Be careful with them suckers! If they are not discharged completely they can sure make you hurt yourself....

Once bit, twice shy.

I have always been a little wary of those things!

If you haven't run it in a few hours the chance of getting zapped are pretty much nil

OK....I replaced the run and start cap with brand new ones.

They were the exact same mfd and vac.

They were both a little smaller than the original ones.

I put them both on and I have the exact same problem. Just a buzz. Again, the pump and motor are both free.

I didn't think they were directional (pos and neg) so I just hooked them up. I hope they didn't need to be hooked up in the right direction and I destroyed them by doing it wrong.

Anyone have any suggestions?

Have you checked voltage ?
May have lost one leg of the 220.

Sounds like the switch isnt engaging properly.

Could also be the pressure switch contacts.

I haven't checked the voltage or the switches. That will be my next step. Thanks.

Exactly what I was referring to.

I'd ohm the motor out, and ohm it to ground. That will tell you if it has an open winding or is grounded. The smoke usually escapes when they go to ground, but an open winding could very well act like that. If it ohms good, then start checking voltage back to the source.

You can always jump across the terminals on a capacitor with a screw driver to insure it is fully discharged. If you kill the power while it's trying to run, it should discharge itself. But if it cycles off, then you kill the power, it can still be hot. Either way, jumping the terminals will insure it's discharged.

I'll check the ohm's as well.

Ohms to ground should show a pretty high value, and ohms across the terminals should show a fairly low value, correct?

Ohms to ground (case/chassis) should be open. Ohms across the windings should be a lower value. Hard to tell exactly without some data on the motor itself.

update ?

Well, I checked the ohms and it showed about 15 ohms across the terminals.

I didn't get any reading to ground.

There is a guy in downtown Corsicana that still runs an old fashion electrical shop. I guess I can take it to him and have him check it out before I buy a new motor.

You are sure you're getting 220v to the motor?

Oh yeah, I checked that as well and it is getting full voltage.

I also completely bypassed the switch by connecting directly to the contacts on the motor and I still had the same problem.

What are the chances of getting a bad capacitor from the manufacturer?

chances are so so, if you don't have a meter that tests capacitors, you can put the meter on ohms and measure the cap, it should build up. if you just get a steady reading, may be a problem.

As far as checking rotation, did you rotate the shaft/pulleys a full 360 degrees?

also, is there a reset on the motor? (usually little red button)

yeah it rotates all the way around and the reset is not tripped. It tripped once when I was messing with it and reset just fine.

aint got no gas in it