I picked up a horizontal craftsman compressor at a yard sale. Looked in good shape. Runs on 220v. I had to add a regulator. Interesting as I got on to post and saw another craftsman compressor question.
The compressor runs fine but when it reaches cut-off pressure the motor stops but air leaks out of a valve attached to the shutoff regulator. The valve has a tube attached to it that goes to the head of the pump. Friend of mine had an exact replacement pressure switch. I tried that one and got the same results. What is also interesting. If you shutoff the compressor with that switch it allow air in the tank to bleed off via that valve. At first I thought that was by design for that compressor. When you flip the off switch something in the switch moves a tab that opens that valve.
I wonder what that line and valve do that goes to the head of the pump? Many other compressors I have looked at have this feature. I figured it was some safety feature.
I wonder what is wrong here. Could I have two bad switch regulators? As stated once compressor reaches shut-off point the motor stop and air bleeds out that valve until it hit the turn on pressure. Seems like this is realted to flipping off the power switch as it produces the same behavior. I had thoughts of replacing this switch regulator with a newer one by using a current model number compressor in Sears. I already got part numbers to change the air intake foam with a round unit that bolts on to the intake air and has a twist off cap that allows for a replacement auto type air filter.
I hope I understand all your problem correctly, and if so, then I know what it is. And it is not the switch. In order to avoid a compressor motor turning on and trying to start the compressor with pressure already in the line from the compressor to the tank, there is a check valve, and when the compressor turns off, there is one brief expulsion of air. Then the check valve stops the air from bleeding out of the tank. At that point, the air "leak" should stop and there will be no pressure in the line until the compressor comes on again.
In other words, I'm reasonably confident that your problem is that check valve. Maybe you need a new one, or maybe yours just needs to be taken apart and cleaned. You should find that check valve at the other end of the tube you mentioned attached to the shutoff regulator.
The check valve is the source if the issue. I did change the switch out with another one and it had its own check valve. I guess there is the chance that I have two bad ones. However, what is odd is a tab inside the switch sticks out to activate the check valve. When you turn off the compressor at the switch the tab moves and opens the valve. It seems that is happening as well once the compressor makes it set high value of pressure.
Well, I guess I'm thoroughly confused. I never heard of a tab in the switch activating a check valve and don't understand how that could be. The only thing connecting my switch to the check valve is a bleeder tube. Of course, there's a bleeder valve at the switch, but that's not the check valve. The check valve is in the fitting going into to the tank. In other words, at the opposite end of the bleeder tube from the switch and bleeder valve.
I'm pretty sure I understand now. It's been awhile since I worked on any compressors. I just went and pulled the cover off the switch on my compressor and ran it through a cycle. I see the "tab" or lever or whatever you want to call it that activates the BLEEDER VALVE, not the check valve. And I'm convinced that your problem is the check valve leaking. When the compressor cuts off, the bleeder valve opens and should stay open. But that lets the check valve close, so with the bleeder valve open, there's no air pressure in the bleeder tube or in the line from the compressor into the tank. And I'll bet your check valve is in about the same place; in the fitting going into the tank.
Thanks, I will give the other end of the tube at the tank a look. I never considered there might be a check valve there. It looked just like a fitting to the tank. Makes sense as I have already replaced the pressure switch and it's attached bleeder valve.
This compressor has two pipes off the compressor. The smaller one goes to the bleeder valve on the shutoff switch. The larger pipe goes to the compressor and that is where the check valve was. I took out the check valve and the ball was missing. Bird you were right. The part from Sears shows about $14. They only do online parts these days. Shipping usually costs as much as the part. Wonder if one could get a check valve locally.
The only Craftsman compressors I've had anything to do with were made for them by DeVilbiss, and the parts were all interchangeable. So if you have a DeVilbiss dealer or service center in your area, you might get a check valve locally.
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