Model #921166400 CRAFTSMAN Air compressor

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Question and Answers

Q:

Pressure relief valve leaks when compressure shuts off. 921166400 Craftsman Air compressor

A:

Thanks for the inquiry and for being a valued member.

When the compressor cuts off, the air in the discharge line bleeds the pressure that is trapped in the line through the pressure switch. This enables the compressor to start back without overcoming the back pressure from the tank.

This is controlled by the check valve that the discharge line attaches to on the tank. A defective check valve will result in a constant air leak at the pressure relief valve when there is pressure in the tank and the compressor is shut off. Drain the tank of air, and then remove and clean or replace the check valve. That will likely solve the issue.

I hope this helps and thanks for using SearsPartsDirect.com. We appreciate your business. 

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Jeff Wallace Sr -
Sears Technician
June 18, 2015
Q:

every time I plug it in it trips the fuse 921166400 Craftsman Air compressor

A:

Thanks for the inquiry and for being a valued member.

I am sorry to hear that the air compressor is tripping the fuse when plugged in. I know how concerning that is to have happen.

You air compressor should be run on its own 15 amp electrical circuit. Make sure the air compressor has a 120 volts supplied to it when it is trying to start. 

If the compressor runs for 5 seconds and then trips the breaker, I would suspect a failure in the starting system. The starting system consists of the start capacitor, the run capacitor, and the start switch. These parts are located on the back end of the motor. When the compressor starts, it can draw double the rated amps. If the start switch does not kick out the start windings, it will continue to pull double the rated amount and trip the housebreaker. If you have an amp clamp and know how to use it, you could check the amp draw of the air compressor. If the amperage does not drop below the amp rating on the compressor, I recommend replacing the capacitor first. If you have a capacitor checker, you can check the capacitor. The rating will be printed on the side of the capacitor.

If you don’t have an amp clamp or a capacitor checker, you can pull the motor and take it to a local electrical supply and have it tested. They will typically test the motor and capacitors free of charge.

If you would feel more confident have a Sears Home Service technician help assist with the diagnosis/repair, you can call 1-800-469-4663, or click here to be directed to the page to set up service.

I hope this helps and thanks for using SearsPartsDirect.com. We appreciate your business. 

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Jeff Wallace Sr -
Sears Technician
January 08, 2015
Q:

Craftsman Air Compressor Model No. 921.166400 won't hold air 921166400 Craftsman Air compressor

A:

Thanks for the inquiry and for being a valued member.

I am sorry to hear that the air compressor is not building any pressure. I know how frustrating that is to have happen.

Your air compressor probably has something broken inside the cylinder. Disconnect the power to the air compressor and remove the plastic cover around the motor and compressor.

Before you take the compressor apart, listen and feel for air leaks. Check to see if air is coming back out of the intake filter. If air is coming back out of the intake filter, something is wrong inside the cylinder. A completely failed part would prevent any pressure building at all, but a sticking check valve or poor sealing pump components might still allow the pump to build pressure to a certain point. Once the pressure reached a certain level it could overcome the seal on the components and prevent them from building more pressure. The result would be partial pressure built-up in the tank.

Turn the motor shaft by hand and be sure the piston goes up and down.

If the piston is ok remove the screws holding the head on top of the cylinder. Remove the head.

Directly under the head is the pressure plate. The pressure plate has reeds on it that direct the air into the discharge line and keep the air from going back through the intake side of the compressor. Check the reeds for warping or breaking. If the reeds are damaged, you must replace the pressure plate. Make note of how the pressure plate sets and the O-rings that seal around it.

Remove the pressure plate and inspect the cylinder walls for scratches or wear, if the cylinder is damaged you need to replace the cylinder, piston, and rings. Make note of the piston and the rings on it. If a ring is worn or broken the air goes back through the intake filter and no pressure is built. If you have to replace the rings, replace the piston and sleeve also.

I hope this helps and thanks for using SearsPartsDirect.com. We appreciate your business.  

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Jeff Wallace Sr -
Sears Technician
January 05, 2015

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