My four-year old PC pancake compressor starts fine but only builds up 60 psi no matter how I adjust the pressure regulator. The compressor motor runs continuously. I checked for air leaks and can't find any. When I use the blower or tire inflator, the pressure drops but builds up to 60 psi slowly. Could it be the pressure regulator or the piston rings?

You can try a new capacitor, or test your existing one.
Plug its power cord directly to an outlet, no extensions, power lost in inapropiate power cords is also a probable cause.
Does the motor turn by hand or is it sticking?
One thing is an electric problem, another would be mechanical.

the regulator does not turn comp ff and on the pressure switch does. If you adjust regulator to 100 psi and the is no air replace regulator or rebuild it, parts are online at several stores you pick on.

is it building up any pressure on the gauge
if the pressure recorded is around 40 psi or less , replace the failed poppet/reed valves in the compressor head
if it goes to 100 psi then replace the automatic controller for the motor

Hi, There are different posibilities. I would need more information. Was it always like that? Does the guage on the main tank and the guage on the regulator both not show more than 20psi? When the auto shut-off is triggered do you feel there is more than 20 psi in the tank?

If your quick coupler is not jammed up, (remove & test) and assuming you are pulling the regulator knob out to adjust the pressure and it is not stripped, you will need a new manifold kit.
There are about 6 versions of this unit so you will need model and type to get the correct part. There are no individual regulator parts available for this unit.

If it's pumping up to 135 psi, shutting off and then restarts at the same pressure point since it was new, the pressure switch may have been set low at the factory. I don't know which model you have but most pressure switches have directions inside their cover as to how to adjust the cut-out and cut-in pressures. Be careful doing this, overpressuring the tank is dangerous. There is an adjustment screw or bolt that changes the pressure on the switch spring. Some pressure switches have two screws, one for cut-in and one for cut-out pressure. A few have one that adjust both pressures. If you do adjust the cut-in/cut-out levels, do it slowly and cycle the motor a couple times between each adjustment to see where it turns off and on. If the compressor is doing what you want it to, only pumping to 135 psi, it will live longer than if you adjust it up to 150 psi. Those last 15 psi of air are hard to get and will mean the motor will be running longer and more heat will be building up in the head.

To increase the life of your compressor you will need to lower the pressure setting of your pressure switch, or replace it with new one that will cut-out at 120. Most compressors have the pressure switch set to cut-out at about 125 psi. Lately, I have seen compessors being sold with factory set pressure from 150 to 200psi. Most single stage compressors can easily handle 120 to 125, however higher pressures are pushing the motor/pump to the limits. This is like driving your car at full speed everywhere you drive. Your car lasts many years because for the most part, you are only uning 20 to 40 % of capacity. Problem is that pressure switch is not really designed to be adjusted (factory set) but not impossible. Look for model number of the pressure switch itself and google for more info. If in fact it cannot be adjusted replace it with generic switch at lower setting. The lower the pressure cut-out , longer life of motor pump. Tiny hole in head is an unloader of sorts and helps the motor to overcome head pressure (yes, this method is less efficient than using pressure switch with unloader valve, however cheaper to build).

The problem with compressors not building pressure is usually a bad pressure switch or bad regulator. Does the motor shut off at 20psi or does it continue running and not build pressure? If the motor continues to run with no increase in pressure, the you should go over the machine looking for air leaks from your regulator back all the way to the motor. Any air leak while the compressor is running can cause the pressure to "peak" way before the intended shutoff that it is regulated to.

I think I follow you... the adjuster over the large screw is used to set your tank pressure but also sets the cut-in/cut-off pressure. You have another regulator to control the pressure to and thru your hose but that doesn't insure that you won't exhaust the tanks supply and use more air than your pump can produce. It doesn't matter what pressure you set it at if your pump can't produce enough cubic feet per minute of air to keep up with your output. If your air use/output is within the pumps output, your idea will work just fine and you can set the hose regulator just below the cut-in pressure but Remember, even a little airbrush uses a lot of compressed air but sanders, grinders, sprayers and impacts use a Ton so don't try this without having somebody monitor the compressor periodically while you try it. It all depends on your air demand.

Check the pressure switch, they can become stuck in the open position. You can jump it to see if it is functioning or use a multimeter if you have one. Assuming that you've oiled and taken care of it it is unlikely that it simly quit, but that could happen... check across the poles of the motor for continuity which will tell you if the electric motor is blown. ALso make sure the compresor is not seized...