Ndfarmer26 - 1/12/2026 07:01
Hello. I have 2007 Peterbilt 379. I was having issues where my primary and secondary air gushes were dropping to 90 psi so I had the compressor replaced. My question is if it’s normal to drop just below 100 psi when the truck is sitting and idling? When I started it up this morning it aired up to 120-125 psi but as soon as I got to where I was going it started to drop. I cannot find any leaks anywhere and the place that replaced the compressor couldn’t find any leaks or any issues. If this is an issue what may be the fix? Thanks!
At 70 or less is usually where your brakes start coming on and the buttons pop depending on the truck.
Why replace the compressor and not the governor? The governor controls when the air compressor kicks on and off. | 
Primary and secondary air guage on peterbilt379
