Model #921153101 CRAFTSMAN Air compressor

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Question and Answers

Q:

Pressure problem 921.153101

A:

Thanks for the inquiry and for being a valued member.

I am sorry to hear of the issue you’re having with the compressor. I know how frustrating that is.

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.

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

If the piston is ok remove the 4 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. Also check the cylinder for scoring, if there is any scoring, I would recommend replacing the piston, cylinder, and the eccentric bearing for the unit. Chances are it will be an issue with the pressure plate and reed valves.

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

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Jeff Wallace Sr -
Sears Technician
June 22, 2015
A:

Thanks, Jeff. I will follow your suggestions. It may be awhile since the compressor belongs to my daughter who lives away from us. Hope to be with her on Sat. 6/27. Will look at it then and report the findings to you.

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joal -
June 22, 2015
A:

Hi Jeff! I removed the top of the cylinder (head) and inspected the reeds. All looks well there. Piston is moving up and down as it should, no restriction or scoring of the cylinder walls. Re-assembled unit. Removed the tube going from the top of the cylinder into the tank at the fitting on the tank and turned the unit on. There is air coming out of that tube. Re-connected the tube and turned the unit on. Still can't get it to build up any usable pressure after running for 5 minutes. Gauge reads less than 10 PSI. What do you suggest to try next?????? Also checked for air leaks all around the unit when it was running and found none.

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joal -
July 01, 2015
A:

in all likelihood, the head gasket is blown, and is leaking between the intake side and the pressure side of the cylinder. that's how it was on mine. why? because the machining on the cylinder head is non-existent, the mating surfaces are rough as a cob, and the little itty bitty surface between the intake and the output was more or less designed to fail, causing the head gasket to fail and also possibly causing obstructions downstream. solution? resurface the cylinder head until there is enough area for the gasket to seat without leaking. do NOT try to get away with just improving on the present skinny/useless gasket surface supplied by the factory. also, the unloader valves on these compressors are generally defective. most of the replacement unloader valves are also defective. thank you, sears! thank you, communist china! if you blow into the intake side of the unloader valve, NO air should come out anywhere. air should only escape when the unloader plunger is depressed, as when full pressure is reached and the unloader is (momentarily) activated. the replacement unloader valve i got was defective. also, the unloader valve is NOT listed on the sears parts list, probably because they're all defective. hope this helps. bottom line is that this series of compressors is seriously flawed by bad parts and bad machining. sears must know that, btw........ sincerely, jeff

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jeff -
November 12, 2015
A:

Hey Jeff, Thanks for the information and suggestions as to how to figure out the bad part(s). I'll be taking this thing apart once more, making a new gasket out of automotive grade material and try to get this thing working. If not, it may be time to scrap it and buy some other manufacturer. Tried one from Harbor Freight. Turned out to be a piece of junk too. Are ALL these things made in China???????

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joal -
November 13, 2015
A:

Makita has a small one similar to this, but I can't vouch for it in anyway. Amazon carries them. They are about `169$ if I remember right. If anyone has any experience with them we'd all like to hear what you think. My Craftsman 3G 1HP bit the dust after only an hour of "on" time over the course of 4 uses since I bought it in the fall of 2011. It looks like new, the oil is perfectly clear the shaft spins and I hear suction and i can spin everything freely, but I heard a big "POP" and saw a spark under the motor or maybe that governor do-hicky set of points inside the fan housing. It blew a breaker. Haven't plugged it in yet since. Checked both startup cap and running cap on a fluke DVM with a cap meter, they read ok. Windings have 4 ohms or so of resistance. Wonder if there was a brown out or something, and I should retry?

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tony -
January 16, 2016
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Q:

oil change 921153101 Craftsman Air compressor

A:

Thanks for the inquiry and for being a valued member.

The air compressor requires SAE30 weight non-detergent oil. I posted an image below that contains the oil specifications. This is covered on page 6 of the owner's manual.



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

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Jeff Wallace Sr -
Sears Technician
May 24, 2015
A:

The bottle that came with the compressor contained 90 ml (3.04 ounces) of SAE Straight 30W Non detergent "one and two stage compressor oil" "that contains an anti foaming agent". O'Reilly auto parts, or anyone who sells oil will have this. It's standard for lawn mowers and small gas engines and compressors.

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tony -
January 16, 2016
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Q:

Air compressor - 921.153101

A:

Thanks for the inquiry and for being a valued member.

I am sorry to hear of the issue you’re having with the compressor. I know how frustrating that is.

If the compressor is not regulating the set pressure of 60 PSI, it sounds like the pressure regulator needs replacement. The part number is E100059.

The cut-in pressure is 95 PSI, and the cut-out is 125 PSI. They are regulated by the pressure switch. I am not showing that the cut-in pressure on this pressure switch can be adjusted. The only way to adjust the cut-in pressure would be to replace that switch with one that is adjustable or that has a lower cut-in pressure rating. I am not aware this type of switch that will fit that model of compressor.

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

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Jeff Wallace Sr -
Sears Technician
March 25, 2015
A:

This is the way all compressors operate. The tank resevoiralways charges to the ~90-125 psi. this is your "store" of compressed air. The second regulator with the set gauge "doles" it out at the correct set pressure. If you set the motor to start and stop at 60 psi the usable regulated pressure would only be a fraction of that, as youneed a reserve to supply the regulated pressure evenly. The motor would also be turning off and on rapidly which could damage it. (if the regulated pressure and the motor set pressure were the same and you tried to use it that way).

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tony -
January 16, 2016
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