Anti-lock Braking System (ABS) — basic information (Transit 2)

Some Transit models are equipped with an electrically controlled anti-lock braking system. The system is activated at speeds above 7 km/h. It consists of an actuator (tandem type booster and master cylinder), hydraulic, electronic units, brake pedal displacement sensor and speed sensors installed on the hub of each wheel. The hydraulic unit includes an electric dual-circuit pump controlled by a speed sensor and a two-valve modulator (one valve per channel). The electronic unit performs several functions: it controls the anti-lock braking system, measures the vehicle speed, monitors the electronic components of the system, and performs system diagnostics. The functions of the electronic unit are constantly monitored by two microprocessors, which also periodically check the electromagnetic valves by sending pulses during the system's operation. The unit monitors the signals sent by the sensors for the purpose of diagnosing faults: if an ABS fault is detected, a warning lamp on the instrument panel lights up and remains lit until the ignition is turned off. A malfunction that has arisen as a result of operation can be identified by a two-digit code stored in the unit's memory. To read the data, a STAR type tester is required, and in the case of a complex breakdown, the car must be delivered to a FORD service station.

The ABS system works as follows: during normal braking, pressure from the brake pedal (and amplifier) closes the master cylinder valves and pressure is supplied through the brake circuits. If, during sudden braking, one of the wheels locks, the circuit inlet valve in the hydraulic unit closes, cutting off the pressure in this circuit. If this does not clear the wheel lock, the release valve opens to reduce the pressure in this circuit and thus prevent the wheel from locking. Both valves continuously and simultaneously close and open to maintain the maximum allowable pressure in the circuit (from the master cylinder), in which the wheel does not lock. When ABS is operating, a slight pulsation occurs in the brake pedal. The pedal displacement sensor monitors all increases in pressure acting on the pedal and switches the pump on and off, thereby maintaining the pedal position and eliminating brake pedal pulsation. During emergency braking, the pedal is pushed back to a predetermined "safe" position. When the brake pedal is released, the ABS system automatically stops working.