"Defective" prim air guage

Note it on the MVIR and document the conversations you had with the people at the company and drive it. As long as you can operate in a safe manner, as long as the low air warning system functions, drive it.

Cover your butt but don’t make it an issue that can turn bad for you.

 

Is there a DOT requirement that the gauge be accurate? DOT requires the low air warning & both brake systems set themselves if PSI is low enough. This isn't a hill I battle over or sacrifice myself on.

 

I'd be curious to know what the actual pressure is.The compressor should cut out at 125-135.Some compressors you can turn up and get 150 if you want,but it would just wear out faster.If the truck was set up to pull doubles it should have a bigger cfm compressor,but a mechanic may have just turned the compressor up for unknown reasons.If the compressor comes on once the pressure drops to 95-105,it's probably ok.Just building more pressure than you need.

 

What does the secondary read?

 

I was driving a 2019 Freightliner,drove it about a year and it had 620 thousand on it.Bossman said to park it and take a newer truck that had 300 thousand miles on it.They sell them when they get to 650,000 miles.The new truck had some annoying issues.The low air pressure came on at 100 psi.So when you released the brakes the air dropped and you always got the warning lights and bell ringing.I asked them to fix it,they mechanic looked at it and said it had to go to Freightliner to get the setting adjusted.Its supposed to come on at 55 psi.The lane departure warnings would go off every time you passed an exit on the interstate.They didn't want to take it to Freightliner so I got my old truck back.
I wouldn't drive it if the primary gauge is faulty.It may or may not pass a roadside.