20 Most Recent Craftsman 3 gal. Air Compressor, 1.5 hp, Horizontal k - Page 6 Questions & Answers

Usual cause is a bad check valve. This valve is usually right where the output from the compressor goes into the tank. Contamination, bad seats, and broken springs are common.

Another less common problem is a leaking cpmpression release valve. You can usually hear the escaping air from these.

Check the head gasket. Mine just did the same thing. Mine was blown between the two chambers on top. It's very thin right there. I went to the auto parts store and bought some gasket and made my own for about $6. It's up a working great...finally. BTW the gasket kit is on back order right now at Sear's parts website. It appears we aren't the only ones with the problem!

It sounds like the small valve that releases the pressure out of the main pipe that runs between the compressor and tank is not working once the tank is full and the motor automatically cuts off. You know this valve is working by the sound of a short spurt if air being released when the motor cuts off. Releasing this pressure means that the motor is able to restart easily because there is no load. If the valve is not releasing this air, the compressor is trying to start under full load which the motor is not capable of doing, hence the humming and popping of breakers due to a current overload as the motor tries to start. Motor burnout is possible if it keeps recurring.

This small release valve is attached to the Pressure control switch that switches the motor On & Off and usually has a small pipe going to it or is incorporated inside the Pressure Control Switch. If the valve appears to be working then it means that the Non-return valve on the input to the tank is not sealing properly and letting air back into the main pipe causing the compressor to start under load. Check both valves for correct operation and replace as necessary.

Easy to check. Follow discharge air tube from compressor to the tank. The brass valve that the tube attaches to is the check valve. You will need some air in the tank for the test. Remove the discharge air tube at tank and spray soapy water. If leaking replace valve or remove and attempt to clean debris. Does not sound like your problem is the valve however. If no leak at valve, check reed valves or head gasket. If your pump is dry lube type, check cylinder for wear / scratches close to top of cylinder. Good luck

You should not have air coming out of the vent cap. From what you've stated here I believe your piston rings and/or cylinder are damaged to where air is getting past them and going back into the crank case. It's possible you have a frozen valve plates so check them on your way to the piston and cylinder.

you have to start at the beginning. your outlet, cord, motor breaker, the on off switch on the comp that trips the comp off at a set pressure. if you know how to use a volt ohm meter that would be good to check the cord and breaker. some time the pressure switch contacts will arc and burn a little and then don't make good contact.

Three things to check.

1) Check that the tank drain is closed

2) Check that your quick connect fitting at the discharge of your compressor is sealing properly.

3) There is a copper or aluminum line that goes from the head of the compressor to the tank. Check the fittings on each end they occasionally come loose due to vibration.

If all of the above is ok:

Check the head gasket of your compressor. The unit you have is notorious for blowing head gaskets.

Hope that helps,
under_psi

Air compressor oil. I prefer synthetic, but you can use regular compressor oil also.

sounds like regulator

I am sure that Sears has there own oil they would prefer you use, If not a quality brand of SAE 30 is commonly used in these compressors.

When a compressor reaches set pressure, there should be a release of air from discharge hose thru the unloader. This release of air unloads the compressor head pressure. The unloader is usually located within the pressure switch. Easy to check. Follow discharge hose from compressor head to tank. There should be a brass/steel checkvalve at the tank. The checkvalve allows air to enter tank, however not allow air to be released back into discharge hose. If this valve is leaking, air will be released from the unloader constantly. Follow 1/4" tubing from checkvalve to unloader and listen for leaks. Repair as needed. If air is not leaking from checkvalve then check unloader mechanism with-in pressure switch. Parts are available at www.toolpartsdirect.com Good luck

Take the exhaust tube from the compressor and run it for a moment or two with your finger over the exhaust port--it should try to blow your finger away. If no pressure, remove the cylinder head from the compressor and inspect the valves in the head assembly. Reeds or discs, if any are cracked or broken, replace same from: Seardpartsdirect.com Make sure the valve seats are in good condition--if not, you may need to replace the cylinder head from the same source. Make sure the piston(s) move up and down when turning the compressor pulley. Inspect the piston top(s) and cylinder wall(s) for excess wear or other damage. The only other problem would be a hissing leak from some tank component. Hope this helps!

Your unit should fill within 5 min. Compressor may have worn cylinder or just leaking. Easy test. Spray soapy water on all connections/fittings including drain valve and regulator while compressor is running. Repair as needed. If no leaks, remove plug from outlet, remove cover and examing cylinder. Turn crank by hand till piston is all the way up into cylinder. Examing carefully the condition of the cylinder close to top. If the cylinder is scratched or worn then pressure is leaking between piston/cylinder and will not fill tank. Replace cylinder kit available at Sears, cost under $50. Good luck with your project.

just make sure you put the port on the right way around and make sure u have the slop then reed then flat, not flat reed flat, or slop reed slop, thats the basic most people make mistake with, then put it together with the outlet pipe off and fire it up and if its blowing and sucking were it is ment to then all good and just check with your hand on the exit hole that the pressur is ther and not going out the intake, hope this helps

sounds like the winding

check head gasket