Air Compressor Not Compressing

[Grimpala]

My dad has a 3 HP/60 GAL Campbell Hausfeld air compressor that appears to have a build date of around April of 2009. Been running fine for years, now all of a sudden it doesn't want to pump past 90-100 PSI.

If you try to start it with 80-90 PSI in the tank the motor will make a handful of revolutions then stall out. If you bleed off pressure to ~60 PSI it will pump up to ~100 PSI before it starts to struggle.

I'm thinking that something in the motor has, or is about to, let the smoke out. It seems as if the compressor part of the equation is working fine, it just doesn't have the oomph to get over that 90 PSI hill.

I told him I'd see what the folks here could come up with before we start firing the parts cannon at it.

Thanks

 

[redmondjp]

First, check for a loose belt (I know, it doesn't make any sense, but having been on this forum long enough I have seen a loose belt cause this type of issue). Second, I would open up the cover on the top of the motor and inspect the exterior condition of the capacitor(s) to see if it is bulging or leaking.

The correct diagnostic tool for this situation is an AC clamp-on ammeter with which you can monitor the motor's current to see if it is exceeding its nameplate rating. Does your motor have a red reset button on the end housing? Any burnt smells coming from the motor?

The other possible cause is a stuck-open or broken output reed valve which then lets tank pressure back into the cylinder.

 

[micromind]

Does the pump have oil in it?

It sounds more like a motor issue than anything else.

If there are 2 capacitors (the humps on top of the motor) one is for starting, the other is for running. If the run capacitor is bad, it'll reduce the HP that the motor can put out. The start capacitor is usually more than 100 mfd, the run one is usually less than 100 mfd.

To test it, you'll need a meter than can test capacitors.

 

[The Cobbler]

first things I would do is check how freely the pump turns with the belt off and check the capacitor(s) are mentioned. also how freely the motor spins ( bad bearings)
it does sound like the motor at this point .

 

[RichWolfson]

Also see if your check valve is functioning. That is my bet. Or the unloader.

///Rich