BRAKE CIRCUIT AND BRAKE VALVE TROUBLESHOOTING
POSSIBLE CAUSES SUGGESTED CORRECTIVE ACTION
TROUBLE: The Brakes are Locked, Service and/or Parking
Parking brake solenoid is de-energized.
Connections to tank and pressure ports reversed.
Parking brake solenoid coil defective.
Parking brake solenoid valve defective.
Tank line is plugged or restricted.
Check power to solenoid
Correct the plumbing.
Replace coil.
Replace solenoid valve.
Remove restriction.
TROUBLE: Both Brake Circuits are Dragging
Tank line has back pressure.
Pedal set screw out of adjustment; residual pressure.
Ensure tank line has no back pressure.
Adjust pedal deadband with set screw.
TROUBLE: One Brake Circuit is Dragging
Obstruction in the brake valve subassembly.
Brake valve is out of balance.
Actuator piston defective.
Brake valve is defective.
A dual relay valve is defective
Remove obstruction.
Adjust balance according to instructions.
Replace piston.
Rebuild or replace brake valve assembly.
Rebuild or replace dual relay valve assembly.
TROUBLE: The Brakes are Not Going to Full Pressure
Internal malfunction of modulating section of Brake
Valve.
Supply pressure is low.
Improper collar adjustment on brake valve.
Remove, disassemble, clean, and inspect brake valve.
Check steering/brake pump system and accumula-
tors.
Adjust collars according to instructions.
TROUBLE: A Low Brake Pressure Warning Occurs When the Brakes are Not Applied
Short in electrical system.
Brake accumulator bleeding down.
Differential pressure switch defective.
Brake warning relay defective.
Check wiring.
Valve Open; close valve.
Check brake valve and dual relay valves; replace
switch assembly.
Replace relay.
J04025 Brake Circuit Checkout J4-9
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