Craftsman 30 gal. upright air compressor, model 919.167311. Air rundown auto start failure.
My problem occurs following initial tank build up. My compressor starts fine on an empty tank and builds pressure as it should. During use, once pressure in the main tank drops to approx. 120 psi, the auto start will engage, but the motor will not turn over to start running. It will simply hum and chug for 2-3 seconds and then blow the circut breaker. If I drain the main tank to less than 10 psi, the motor will start normally. I have removed the check valve and inspected same. It looks new in appearance and the disc appears to be white and in good shape. I took a screwdriver and checked for free movement. The spring seems to have proper tension, compressed freely and nothing seemed to be sticking. I reinstalled the check valve and left the pressure relief tube unattached at the pressure switch. I turned on the compressor and had a steady pulsation of air coming from the tube. The compressor would only build approx. 20 psi. while this tube was disconnected. I turned the compressor off and the check valve held back the 20 psi with no signs of a leak. At 20 psi with the pressure relief tube disconnected the motor would start with no problem. I reconnected the pressure relief tube at the switch, and with the 20 psi in the tank, the motor would not start, hummed and chugged until blowing the circut breaker. I believe my problem may be the switch, but with a nonreturnable $91.00 part, I don't want to just jump right into that if it may not be my problem. If there may be other causes with returnable parts, I would obviously prefer to try those first.
Jackie s
Maestro
No worries! Manage My Life is here to help! The experts offer great advice and would be glad to assist you. It usually takes 24-48 hours to receive a response. Have a great day!
Sam a
Expert
Thank you for your question on the air compressor not restarting on demand. I can understand not wanting to purchase a part that you do not need and not being able to send it back.
The problem you are experiencing is that the head pressure relief valve is not working when the air compressor reaches it target pressure and shuts off.You should hear a whoosh of air for about 2 to seconds after it shuts off and that is relieving the head pressure off the head so it will be able to restart as needed. There is a mechanical arm inside the pressure switch that when the pressure switch is satisfied and shuts off it opens the head pressure relief circuit and unloads the air from the small tubing from the check valve to the outside. If the check valve was bad it would either stall the motor at about 40 psi or it would be leaking through the small tubing for the pressure relief when you have it disconnected when the compressor is off. I realize that this is a $92.00 part but it is a very high probability that replacement of this part will correct the problem you are having with start up.Thank you for using Manage My Life. Sam A.Joe
Newbie
Thank you Sam. That is the reassurance I was looking for. I'll give it a shot.
Joe
Newbie
Sam, I received the switch yesterday and installed it last night. However, that did not correct my problem. The compressor is still acting as explained in my previous question. Where do I go from here? I do hear the whoosh, or hissing sound that you mentioned should happen when the compressor reaches target pressure and shuts off. But I heard the same sound with my orginal switch. I do not hear any obvious leaks when the compressor shuts off. Looking for further direction.
Sam a
Expert
I am sorry that this switch did not correct the problem. Since you had examined and check the check valve thoroughly I was pretty sure it was the pressure switch. I am sorry that it was not the case. You could try to open the fitting on the small tubing where it meets the pressure switch after the compressor shuts off. If there is no air coming out of that tube then the check valve is bad and not unloading the head pressure. When the air compressor runs the check valve should pulse to put the air in the tank and then with the compressor shuts off it should hold the air in the tank and release the air from the pump head through the small tubing to the pressure switch. There has to be pressure in the small tube for the switch to know when to shut off. Maybe we should have gone with the check valve first. I do not like guessing either. A19712 CHK VALVE 1 15.49 Let me know what you have found. Sam A.
Joe
Newbie
Sam, the check valve also did not correct my problem. I am having the same exact issues as before. So I've tried the switch and a check valve. Neither has corrected the issue. So what next? Where do I go from here?
Sam a
Expert
Wow! This one is getting to be a real challenge. If the compressor will start and run, starting from an empty tank is the compressor unloading when it shuts off? If it is then, it is rare, but you could have a start capacitor going bad. Usually the motor will just not start if the capacitor is bad, but in this case the problem may be the more you attempt to use the compressor the worse the capacitor is becoming. So please remove the caps from the top of the motor and check them, or have them checked. If you find the start cap is bad then send me the information on the motor and I will see if I can find a cap kit for you. Give me the brand of the motor. It could be an AO Smith a GE or a WEG motor and it will have a D number on the motor plate. To check the capacitors, use a multi-meter with a capacitor checker mode. This will require a location mode on the meter that will load the cap and then it should bleed down. I am running out of solutions but this could have been the problem all along other than the motor slowing going bad. Sam A.
Joe
Newbie
Sam, it sounds like the air compressor is unloading when it shuts off by the wishing sound it makes. The motor seems to be running fine, just as it always has since new. I took off the cap from the top of the motor. I'm assuming the compacitor is the aluminum cylinder shaped device 1 1/2" in dia by approx. 2 1/4" in length with two wire feeds. Looking at I don't see problem as the wires are securely in place. But I understand it could look like new but not work like new. I will have to find a multi-meter as I do not own one. But anyway, if you would like to assist me in finding a capacitor, my motor is a AO Smith, #D27266, Ser.# K56B04B23. Thanks again.
Sam a
Expert
Thank you for the update on the compressor. It sounds like it is doing what it is suppose to do when it shuts off. The start capacitor kit for this AO Smith motor is part number D21477. I hope this will help. Sam A.
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