Stop Lights Switch - Fiat Bravo Service Manual

Bravo-Brava
Braking system
Anti-lock braking system
33.
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Sensor/phonic wheel
on rear wheel
1. Sensor
2. Phonic wheel
3. Hub
4. Brake drum
5. Suspension arm
If one or more phonic wheels break or become deformed, causing a difference in speed of 25% in rela­
tion to the reference speed, the electronic control unit switches off the device and switches on the fault
warning light. The time for detecting the fault is about 120 seconds with a vehicle speed of over 6 km/h.
NOTE Whenever fitting an rpm sensor, smear it with water-repellent grease, otherwise it could be da­
maged during subsequent withdrawal as a result of temperature variations over a period of time.
STOP LIGHTS SWITCH
The signal that the brake pedal has been operated reaches the control unit by the connection of the
switch (1) controlling the stop lights to pin 12.
This information is useful not only for controlling
braking, but also under particular conditions, for
example if sudden acceleration which makes the
wheels skid is followed by heavy braking, or in the
case of rough road surfaces (bumps etc.) which
could cause variations in wheel speed for reasons
not associated with the braking in progress.
Under these conditions the microprocessors work
out a strategy linked to the changes in wheel
speed at these moments, ensuring that braking is
within correct parameters. As these are particular
circumstances of braking control, the efficiency of
the system is not impaired if the brake pedal switch
is not connected to the control unit. For this rea­
son it is not indicated by the warning light coming
on, nor is the A.B.S. disabled.
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