RAM 2500 Van V8-5.9L VIN Z (1997)
Brake Warning Indicator: Description and Operation
Brake Warning Lamp Description
SYSTEM OPERATION
The brake warning lamp gives an indication when the parking brake is applied, when the pressures in the two halves of the split brake hydraulic
system are unequal, or when certain problems are detected in the Rear Wheel Anti-Lock (RWAL) or Anti-Lock Brake Systems (ABS). The lamp
is turned on when the ignition switch is turned to the Start position as a bulb test. After the bulb test, the lamp is controlled by hard-wired inputs
from the parking brake switch, the brake warning switch, or the RWAL control module/Controller Anti-lock Brake (CAB).
The brake warning switch closes to ground when it senses unequal hydraulic pressures in the two halves of the split brake hydraulic system,
possibly due to low brake fluid level or brake fluid leakage. The parking brake switch closes to ground when the parking brake is applied. The
RWAL control module or CAB can also turn on the brake warning lamp if certain brake system faults are detected.
SELF TEST FEATURE
The red brake warning lamp is connected to the parking brake switch and to the pressure differential warning switch in the combination valve. The
red light illuminates for approximately 2 - 4 seconds at engine start up. This is a self test feature designed to check bulb operation.
REAR BRAKE CIRCUIT
The red warning lamp illuminates when the parking brake is applied. It also illuminates if a fluid pressure drop occurs in either the front or rear
brake hydraulic circuit. A pressure drop moves the valve in the combination valve toward the low pressure side. When the valve moves it pushes
the pressure differential switch contact plunger upward. This closes the contacts and completes the circuit to the lamp. The lamp will remain on
until repairs are made and normal fluid pressure is restored.
LAMP ILLUMINATION
The brake warning lamp illuminates when ignition voltage is supplied to the bulb and a ground is provided for the bulb. The bulb has ignition
voltage supplied to it any time the ignition switch is in the RUN or START positions. A ground for the bulb is provided by the:
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Ignition switch during the START mode
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Parking brake switch when the park brake is applied
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Brake warning lamp switch when a hydraulic fault has occurred
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Controller Antilock Brake (CAB) during diagnostics and when a RWAL fault has occurred
