Air Compressor Stalling

[spasm3]

I have a Kobalt single stage 60 gallon cast iron oil compressor. Couple of years old. I don't know if lowes even sells this model now.

It will run fine with no load. It will run fine till it hits 80psi, then it slows down until it tries to slip the belt. It should pump the tank to 150psi or so.

I don't know a lot about compressors. does this sound like something i can diagnose and repair?

Thanks.

 

[Propflux01]

When it slows down, does it seem like the compressor itself is slowing it down, or just the electric motor seems like it just cant handle the load?

 

[clinebarger]

Check the belt first.....It won't squeal like a V-belt on a vehicle. Glazing of the belt traction surface is pretty easy to spot.

 

[spasm3]

It sounds like the electric motor is trying to turn the compressor to the point of slipping the belt. Almost like the compressor is seizing up. Its always at 80psi when it starts. The electric motor tries to keep turning the compressor until the belt squeels.

Its never been run low on oil and really has not been run that much.

Runs flawless to 80psi, but won't pump past that. The electic bogs down and it squeels right before it trips the breaker.

 

[Rand]

Most likely some kind of issue with the motor. Bad bearing? bad winding/wiring etc.

Its 240v?

 

[spasm3]

Originally Posted by Rand
Most likely some kind of issue with the motor. Bad bearing? bad winding/wiring etc.

Its 240v?



Yes 240

 

[Chris142]

Have you tried tightening the belt?

 

[CDX825]

Had the same problem with a friends air compressor and it was the valves. We got a rebuild kit and for it with new valves and that solved the problem.

 

[demarpaint]

As mentioned I'd check the belt. Did it start doing this with the cold weather? I have that compressor and a small Craftsman belt driven compressor that gave me a similar problem in cold weather. Believe it or not I changed that machine over to a synthetic compressor oil and haven't had the problem since.

 

[Donald]

Check belt. There are still places that rebuild electric motors and would probably check yours at no cost? If its the compressor itself then there maybe rebuild kits available, or a new compressor. Kobalt did not make the unit but had a company put it together with available parts.

You almost certainly have a good tank and either a good motor or compressor.

Stop by your local indy shop, ask them who services their compressor and ask that company for advice.

 

[zzyzzx]

Are you sure that you have a good electrical connection? For all I know, you are only getting one leg on your 240V circuit. Unlikely, but really easy to check.

 

[JC1]

Originally Posted by demarpaint
As mentioned I'd check the belt. Did it start doing this with the cold weather? I have that compressor and a small Craftsman belt driven compressor that gave me a similar problem in cold weather. Believe it or not I changed that machine over to a synthetic compressor oil and haven't had the problem since.


+1 on using synthetic oil in your compressor. The past two weeks as the temperature dipped down my compressor runs slower for the first 5 minutes then by the time it warms up it's running normally. Even if Lowe's no longer sells that model, most Air compressors have the same basic design.

 

[Fitter30]

If you remove the air fi!ter and block the intake for a few seconds this will unload the compressor and then if it starts knocking it could be a mechanical issue.

 

[wag123]

Check/Replace the motor run capacitor. This is something that will cause this kind of problem and a part that commonly fails (because most of them are low quality Chinese parts now days) .

 

[ragtoplvr]

Replace motor run capacitor first if it has one. Most, but not all 150 PSI compressors are 2 stage. One big lower pressure piston and one smaller high pressure. If the high pressure one has a valve problem, then the big one is attempting to pump up to 150, and it is too big and too much work. This compressor may be reed valve, and it is not uncommon for a discharge reed valve to break. easy fix. If it is disk valve, they sometimes get some rust and seize in the bore. Either way off with the head. New gaskets are recommended.

Rod

 

[spasm3]

Originally Posted by demarpaint
As mentioned I'd check the belt. Did it start doing this with the cold weather? I have that compressor and a small Craftsman belt driven compressor that gave me a similar problem in cold weather. Believe it or not I changed that machine over to a synthetic compressor oil and haven't had the problem since.



Thanks, i've had amsoil compressor oil in it since the break in instructions. The belt is tight. I'm going to go through this list then maybe pull the head.


https://mastertoolrepair.com/images/Troubleshooting your compressor.pdf

I don't think the electric motor is the problem.

 

[spasm3]

Looking at the diagram below, i'm wondering about part number 6 the quad valve plate assembly.

https://mastertoolrepair.com/60-gal...parts-vt636201-vt636201aj-p-1389147.html

 

[Dinoburner]

Once had a faulty check valve going into the tank that didn`t open all the way. Also have had a bad capacitor that would get very hot. The motor groaned also. From the OP`s symptom seems to indicate a mechanical issue.

 

[meep]

belt should not slip, so it needs to be tightened.

run capacitor is suspect - the motor will not have full power, will hum louder, and generate excess heat without it.

I'd also pull the belt and make sure the pump turns smoothly.

 

[spasm3]

Since several have suggested the capacitors, I'll start there! And check the belt.

Thanks