motor slows down with just a little pressure?

by John
(Texas)

I bought a older Sears 5 hp compressor, model #919-176850. I tore it down and cleaned everything I could. Replaced all new gaskets. Changed oil. When I started it, does good when it's not building pressure. As soon as it gets around 10psi the motor starts lugging and almost stops. Does this sound like the check valve is clogged or what else should I check? Thanks.....John.....


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Bill says....

Hi John. If the intake and pressure valves are OK, yes, do tear down and clean the check valve.

If that doesn't make change, and assuming there is nothing of a mechanical issue remaining, I would look to either the start or run capacitors, or the motor itself as the source of the problem getting your air compressor to run.

Cheers,

Bill

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Sears compressor takes forever to fill....?

5 hp air compressor takes 30-45 minutes to fill 33 gallon tank!

It's a sears model and I am not sure if it is supposed to take so long. Could it be the valves, or piston rings. I should say that it does eventually reach the 150 psi it is supposed to.





Bill says...

Howdy. I'd look to the intake valves first. If they are starting to get get wonky, they could be bleeding some of the compressed air back to atmosphere while at the same time, allowing only a portion of the compressed air into the tank.

That may be why it takes so long to fill.

The intake valve port is supposed to allow air into the compressor head, and if you are feeling a "puff" of air back out of that hole each time the compressor piston cycles, that would indicate that the valve inside is failing.

Check this out first.

Cheers,

Bill

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Will not build pressure. Motor cuts on & off

by Mark

I have a 2HP 15 GAL 110v single cylinder oil-less Craftsman air compressor that does not build maximum pressure. It will get up to about 45-55psi and then cut off. It then continues to cycle on and off in about 5 second bursts. I haven't been able to get the motor cover off yet because it requires a long Torx screwdriver. I don't want to put much into it and can always use for parts but it is handy.
Your help would be appreciated!

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Bill says...

Hi Mark...

If your compressor was mine, I'd be looking to the pressure switch.

If you have the skills, unplug the unit, dump the air, bypass the switch, and see if that solves the problem.

Or, just spend the $30 or so for a new one, and if that isn't the problem, now you have a spare. :-)

Cheers,

Bill

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