Air compressor does not shut off at 150 psi - Dewalt Heavy Duty 2 Brad Nailer Compressor Combo Kit

Most pressure cut off switches have an adjustment screw on them where you can dial in the cut off/turn on pressures. Take a look and see if you have the adjustment screws. If you have the switch model, you can try looking up online to see how to make these adjustments.

replace the non-return valve in the pipe at the tank connection
air out of intake is poor poppet/read valve seating and pressure in the sump is the tank air leaking back and down past the rings
150 psi is excessive and not good for the compressor so adjust it back to 100 -110 psi

home compressors should cut out at 100- 110 psi so check / replace the controller
air out of the inlet is air under pressure holding the valves open
pressure in the sump is a blocked breather for the sump possibly from excessive air pressure
remember it is not pressure that drives tools but volume flow so if you have a 10 cubic ft /min compressor but are running a tool that requires 12 cubic ft /min air then 150 psi is not the answer
a bigger capacity compressor is

A regulator controls the pressure in the air line leaving the compressor and does not affect when the compressor turns on or off.

The pressure switch monitors the pressure in the tank and turns the compressor motor on and off when the switch closes or opens in response to changes in the tank pressure. If the compressor does not shut off, it is possible the pressure switch has been set to a pressure level that is higher than the compressor is capable of attaining, thus it does not shut off.

The compressor is capable of developing 150 psi and is noted as having a "120 psi cut-in pressure". When you say it doesn't shut off, does that mean it will generate 150 psi or more of pressure and fails to shut off or it develops less than 150 psi and does not shut off.

If the compressor does not generate 150 psi, then it is probably somewhat worn out and not capable of developing enough pressure to meet the factory high pressure limit. I would try adjusting the pressure switch upper pressure limit down to 130 psi or less (less if the compressor will not develop 130 psi) and see if this solves your problem If it doesn't,

If the compressor will develop 150 psi or more, then try adjusting the high pressure limit to less than 150 psi. If you can't adjust the high pressure limit then the pressure switch is defective and needs to be replaced.

Try tightning your regulator all the way, then loosening, then see if air passes thru

The compressor has a max psi setting of 150.If the pressure is not reaching this or is only stabilizing at a low pressure you have an air leak around a gasket somewhere.If it is reaching 150psi and not shutting off your pressure switch is bad.Replace it.Check your owner's manual for a part number or go to www.factoryauthorizedoutlet.com to find the part.

YOU WILL NEVER GET 150 UNLESS YOU PUT A DIGITAL GAUGE.

The pressure controller is bad, so change it.

Pressure switch may be stuck. May need to adjust pressure switch.

sounds like the pressure switch is fused shut, more than likely it needs to be replaced, most single stage pumps should shut off at 125 psi max.