peterbilt air leak

I’m used to the pre 379 stuff so i may be wrong about it being a trailer circuit pressure only switch on that. All the 351/352/358/359 stuff we’ve owned over the years have had 2 seperate low air switches and brake light switches. Both connected to one buzzer. That way if trailer curcuit gets severed it applies brake lights on trailer and buzzer. Also it would light up brake lights if key was on and park brakes were set. (That is one reason why they were unhooked.) parked at night too sleep burning hot side of bulbs would melt the lenses.
On Pete’s One would be on manifold on firewall under hood and the other would be on manifold under dash next to buzzer.
On the White 4000’s and White-Western Stars we have they were located under a fiberglass cover next to driver seat.

 

Things were different on brake stuff back then. Most trucks didnt have any tailights on rear of tractor from factory. Grand pa bought 3 ‘74 359’s new that had government mandated anti-lock brakes on drives. None on steers. Those Anti-locks were dangerous and by ‘78 manufacturers were recalling every truck to snipp the wires and remove the boxes on the frames. Air System was tractor on one and trailer on the other. Not tractor steer and trailer on one and tractor drives on the other.
And yes brake lights would be lit with park brakes on if key was on.

 

I have a Peterbilt factory manual. You can purchase one from peterbilt. They aren't cheap tho just FYI.