Ingersoll 5HP compressor about 15 yrs old.
Last summer I found it running away – smoke was everywhere, the compressor hot enough to boil water. Shut it down, took to compressor repair shop, they said the unloader valve failed. They replaced regulator and it ran fine for about 6 months.
A couple weeks ago it wouldn't turn on until I pressed the reset button on the motor. Today was the second time, when I hit reset button on motor, it started up, & seemed to run fine and made pressure, except it wouldn’t turn off.
What got my attention was I heard air leaking while it was running. I found it was coming from the unloader valve. When I shut it off, the unloader valve closed after a few seconds like normal.
I should mention about 2 months I replaced regulator because the on-off lever broke. It was running ok at the time. I replaced it with the same model the comp shop used.
I will say the regulator is a Pumptrol, not an IR original, but I figured the comp shop knew what they were doing. The cutoff pressure is 150.