Fiat 1998 Marea Weekend, Service Manual

Page: 444 / 846

Braking system
Anti-lock brakes
Marea - Marea Weekend
33.
On the basis of the signals received from the rpm sensors on the front and rear wheels, the electronic
control unit operates the electro-hydraulic control unit which, in turn, varies the pressure of the brake
fluid sent to the calipers in accordance with three stages: pressure increase, maintenance or decrease.
Pressure increase stage
1. Electronic control unit
2. Low pressure accumulator (reservoir)
3. Recovery pump motor
4. Recovery pump
5. Restricter
6. Brake pump
7. Brake servo
8. Multi-polar ring
9. Pressurizing solenoid valve
10. Discharging solenoid valve
11. Brake caliper
12. Rpm sensor
13. Single-acting valve
When the driver presses the brake pedal, the pressure produced by the brake pump (6) reaches the brake
caliper without undergoing variations, because the solenoid valves (9) and (10) for the hydraulic unit
are not connected to earth by the electronic control unit.
When the braking force increases, the deceleration of the wheel consequently increases: this causes a
faster deceleration of the vehicle (i.e. the slipping of the wheel increases).
The value of the creeping should not exceed a given figure beyond which the wheel loses its grip with
the ground and starts to slip, losing direction and increasing the braking distances.
The rpm sensor (12) signals that the deceleration values reached could adversely affect the adhesion of
the wheel to the ground: at this point the electronic control unit (1) commands the electro-hydraulic
unit solenoid valves, reducing the braking force and allowing the speed of the wheel to increase to re-
cover its grip.
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