Organizational Troubleshooting Table
TEST OR INSPECTION
ELECTRICAL SYSTEM - continued
ONE OR MORE LIGHTS DO NOT LIGHT - continued.
Check plug and/or receptacle for dirty or corroded contacts.
Clean contacts, if dirty or corroded.
If contacts are not dirty or corroded, go to step 6.
Check for loose or broken ground wire at light assembly.
Repair or tighten ground wire, if defective.
BRAKES WILL NOT RELEASE.
Check for defective emergency relay valve.
Build up pressure in semitrailer brake system, if semitrailer is
coupled. Open drain cocks on semitrailer air reservoirs, if
semitrailer is uncoupled.
If emergency relay valve is operating, go to step 2.
Check air hose connections to towing vehicle.
Connect air hoses properly.
If air hoses are connected properly, go to step 3.
Check position of brake valve on towing vehicle.
Move brake valve to release position.
If brake valve is correctly positioned, go to step 4.
Check for restriction in service air and emergency air lines.
If air lines or hoses are restricted, replace or repair as
If air lines or hoses are free of restrictions, go to step 5.
Check for closed shutoff valves on towing vehicle.
Open valves, if closed.
If valves are open, go to step 6.