Windstar V6-232 3.8L (1995)
Brake Fluid Pressure Sensor/Switch: Description and Operation
The Brake Pressure Switch (also called the Deactivator Switch in the Cruise Control System) provides input to both The Antilock Brake (ABS) System
and the Cruise Control System.
NORMAL OPERATION:
Antilock Brake (ABS) System
A brake pressure switch is used to inform the ABS module of vehicle braking in the event the zero position brake switch is defective. The brake
pressure switch is a normally closed switch. The ABS module receives a 12 volt signal through the switch, with the ignition switch is in RUN.
During a braking event, at a predetermined pressure, the switch opens and the voltage signal goes to 0 volts.
Cruise Control System
The Brake Pressure Switch is an additional speed control deactivation device should the brake switch fail. Depressing brake pedal with sufficient
pressure to create 125 psi in brake line, causes brake pressure switch to open, thereby removing current from speed control servo.
The deactivator switch:
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is a normally closed switch.
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replaces the speed control dump valve as a redundant safety feature in the system.
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under normal conditions, when the brake pedal is applied, an electrical (brake on/off) signal from the stop lamp circuit to the speed control
servo will disengage the system.
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under increased brake pedal efforts (22-44 Nm [5-10 lbs] engine running), the deactivator switch will open and remove power to the speed
control servo, releasing the throttle from servo control.
FAULT DESCRIPTION:
Hydraulic pressure switch is determined to be either continuously on (0 volts) from ignition power up or toggled on when the brake switch is off and
the vehicle is accelerating.
POSSIBLE CONTRIBUTING COMPONENTS/VEHICLE WIRING CONCERNS:
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Short to vehicle ground or open in the wiring between the hydraulic pressure switch and the anti-lock brake control module.
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Pressure switch shorted to ground or open.
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Defective anti-lock brake control module internal circuit.
