[Chester Stone]

Chappell, with your compressor starting up after an hour and a half, you likely have a leak, but not enough to change the gauge every minute. First, I would check to be sure there is no water in the air tank. Secondly, you can purchase a cheap air gauge to install in the air tank bay at the "T" just above the cut off switch. At the moment I cannot recall the brand, but you can purchase from Harbor Freight a tool that can hear an air leak that the human ear cannot. This tool helped me locate many air leaks and my compressor seldom runs now.