Thread: Learned something about air compressors.

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Since most of us have air compressors I thought I might pass along something I learned yesterday. You might remember I was having trouble with the motor on my air compressor failing, and Eaton supplied a new one at no charge. We put the new motor on and after using it several times we started blowing fuses. ( My switchbox has two 30 amp fuses in it) Also, when it would come up to pressure and shut off the little check valve on the square D switch would keep hissing, releasing air until the pressure would drop and the compressor would kick on again.

Yesterday I decided to fix the problem so I took off the lid from the square D switch and headed to our local industrial supply company to see what I needed to fix the problem. Ran into a very knowledgeable guy there who told me what was going on. There is a check valve on the inlet to the tank, it's purpose is to let air into the tank, but once the compressor shuts off it traps the air in the tank. Right above that is a bleed off line that goes to the square D switch. It's purpose is to relieve the air pressure off of the cylinders so that the motor can more easily crank the compressor when it first fires up. The check valve isolates the tank air from the cylinder pressure so that only the cylinder pressure is released upon shut down.

He said the reason I was blowing fuses (and probably why my first two motors failed) was because the check valve had failed and the line that was supposed to relieve cylinder pressure was unable to do it's job, so when the motor kicked on it was having to work very hard to get the compressor to turn over that first few revolutions (too much cylinder pressure). That was overworking the motor and causing the fuses to blow too.

I replaced that check valve (when I pulled out the old one it was rusted from moist air going over it, and also the seat was crooked from corrosion) and now the compressor comes up to pressure, shuts down, and I can hear the bleeder momentary hiss until all the cylinder pressure bleeds off. My compressor also fills up faster now because the check valve being rusted was somewhat restricting air getting into the tank.

Like I said, I know most of us have air compressors and thought you might want to keep this in mind in case you ever start having similar problems.

Don