In the middle of body work and .....

[sixnine]

...my air compressor won't shut off!!!! I was using my die grinder to knock down some spot welds. I was doing my usual work a few minutes, wait a few minutes (the die grinder is a cfm killer) and noticed that the compressor was running longer than it usually does. I stopped the grinder and waited a few minutes...compressor is still running and the psi guage isn't moving. The pump was extremely hot, so I manually shut it off, but now I'm stuck with a half body worked car until I figure out the air comp. How do I know if the cylinder is bad? Could it be a bad psi guage causing the auto shut off to not work correctly? The air in the shop is hot and humid, will that affect "pump up"? The compressor is a 7hp 60 gallon Kobalt model from Lowe's. I've only ran it about 10 hrs total. Anyone have any ideas?