diagnose my air compressor

[Haywire]

My compressor got rained on. What it's doing is this. If the tank is empty and you turn it on, it pumps up to 150psi like normal. If it's got 75 in it, it acts like the motor doesn't have enough power to get the pump going. It turns over a couple times and hums like it's locked up.

What do ya think?
Ian

 

[vwnotrunning]

Your unloader is not functioning. Typically there are two types. One is just a check valve at the tank inlet with a bleeder orfice hole. Some use a valve / solenoid activated by the pressure switch. Both options allow the air to bleed off between the compressor and the tank. Then the compressor starts with no pressure to minimize the startup load.

 

[RobertBrown]

Your unloader is not functioning. Typically there are two types. One is just a check valve at the tank inlet with a bleeder orfice hole. Some use a valve / solenoid activated by the pressure switch. Both options allow the air to bleed off between the compressor and the tank. Then the compressor starts with no pressure to minimize the startup load.

x2
When the pressure switch cuts the motor off, you sould hear a Ssssssss as the air trapped between the motor and the check valve is released. I don't know why rain would cause this to fail but I agree vnotrunning. It sounds like the unloader is not working. Typically, it's a shrader valve on the switch, sort of like the valve on your car tire.

 

[dex3361]

The unloader valve relieves the pressure off of the head of the air compressor so it will be easier to get rolling. Graingers has them fairly cheap.
Unloader Valves Yours is likely one the ones listed as a load genie.

 

[5030]

.......... and easy to replace and cheap, compared to the motor which you'll burn the start windings out of doing what you are doing......

 

[bindian]

Tap on it lightly with a hammer or a block of wood. Spray some lubricant on it and try it again.
hugs, Brandi

 

[Haywire]

Thanks... I'll check it out this weekend.

Ian

 

[jinman]

A few more random things. . .

You aren't running it off an extension cord are you? Many extension cords are 16 gage wire. None of my compressors will run off of a long extension cord unless I use the one with 12 gage wire. Even then, the compressors are hard starting. If I were you, I'd try another power outlet also. If your outlet is not making good contact, you could be loading down the connection and maybe even causing heat build-up in your wall socket or wiring. There's a remote chance that you need a fresh/new starting capacitor too. Those are usually a snap to change on an air compressor.

 

[Bird]

I thought the first four replies sounded right . . . . . except I couldn't figure out how getting rained on could cause that; maybe just a coincidence that it happened after a rain.

But now I think Jim (jinman) has a couple of very likely culprits.

 

[mbrule]

yep, what everybody else said.

Then, don't leave it out in the rain.... LOL