well we have tried 3 scanners no communication... so with out chasing that problem, we checked the basics fuses ect. no go.
abs light and brake light where both previously on.
customer had issue with air pressure sensor leaking air though the sensor its self, changed them all good.
customer blew a brake line few months ago, we changed it and had a hard time bleeding it and getting a good pedal. after bleeding it 100 times it was good. so 2 month later now the customer blew another brake line in a different state, had it repaired and was on his way. this issue began after that. brakes seem to work fine.
truck has a single air tank, 2 gauges primary and secondary both read fine. I assume the tank is split on the inside, I changed both air pressure sensors when I took one out there was no air and the other one was full pressure, therefore I am thinking we have an air supply issue to one of the brake boosters. we have 2 boosters 2 masters next to the air tank on the passengers side.
my question is, how do I go about diagnosing an air supply issue, do I remove the line to see where I have pressure and where I don't? some of the air lines are very rusty so I would rather not go that path the whole way. I have sprayed everything down with pb blaster. there seems to be an air switching valve on the frame I am not sure if that could be bad or if I have a bad brake booster. if you have any diagrams or path of air flow that would help us out. thank you.