40400 Compressor Hums

by Richard
(Falls Church, VA)

My 40400 hums when turned on. I opened the shroud looking for the reset switch and could not find it. However, the fan blades will difficult to rotate.

I have reviewed the trouble shooting section on this forum and cannot find my problem and the solution. Any thoughts?

Also, it is possible the compressor ran with no oil by the previous owner.


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Dec 05, 2016
Humming 40400
by: Bill

It's humming because it cannot start.

That the fan cannot be turned suggests a mechanical issue with the pump being seized, and since the fan is typically on the same motor shaft, the fan blade is difficult to turn.

Or, it could be the caps.

Please see : http://www.about-air-compressors.com/humming-air-compressor.html

for more things to check.

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