Originally Posted by BaileyB
I am working on a 2000 Int school Bus 3800 series
Parking brake will not release. Air pressure is 120 .
Found electrical air solenoid not functioning no electrical input. solenoid removed solenoid test good .
Does anyone know where I might find a electrical diagram to trace the circuit
Thanks in advance for the Help
I can't help with diagrams, but it would be good to verify exactly which brake system you have. Is it a standard air brake system, or a hydraulic system with an air parking brake? The parking brake hand valve on most systems should have a direct air supply and output to the air spring.
A solenoid being part of the system suggests it may be hydraulic with air parking brake, unless it is part of an interlock system. I would check for anything that looks like a brake master cylinder (a manual transmission may have a separate smaller one for the clutch).