Just had a new air compressor put on a year ago when Peterbilt did a new long block it will charge up to 120 and slowly drop to just above the 100 mark it won’t go back up again until I get below that 100 mark which is where I assume is where the auto fill is set at to kick back on and run it back up to 120’s so It basically runs at like 103… My auto air tire light on my trailer will randomly kick on. As I again assume they are dropping down to this same 193 mark and then when I drop the air below the factory set limit. It runs everything back to 120 and then back down to that 103 I cannot find a leak and I had new steers out on at a TA and they couldn’t see a leak anywhere either doesn’t mean it’s not there But could this be the issue? or is this a compressor issue? and can I set it somehow? it does get to 120’s. Just doesn’t stay. But it stops at like that dumb 103 mark Amy thoughts?
Separate the tractor air lines from the trailer and see what happens. Build the air to 120 and then turn the truck off and walk around and listen. If it goes to 120 and then drops to 103 the air is going somewhere, maybe a slow leak in a tire. Assuming the gauge is correct. What model air dryer do you have? Bing Videos Very short video shows how to turn off the auto inflation air. You can try this and see if anything changes.
Air drier or leveling valves are the first things to look at. Both can be problematic. If the truck is sitting still and it holds, most likely the leveling valves. The auto inflator system may also have a leak in the system. The light should come on for a minute or two when first starting the truck, that’s when it runs the self test. Unless you have a low tire or a leak, it should not come on after that.
My first tbought would be a leaking tire, or lealing thru tee on the auto inflation. You're losing air, the light randomnly comes on, etc. Couple of symptoms that make a plausible guess. But it sounds like your compressor is doing exactly what the governor is telling it to. The constant cycle is from a leak
If your trailer inflating system has high/low regulators, it may feels like your 'high' regulator is bad or faulty dump valve keeps dumping air until 103psi where 'low' air regulator kicks in to stop the dumping.
