Operation; Noise Detector Safety System - Fiat Brava Service Manual

Electrical system
Electric windows
55.
OPERATION
The electronic control unit on the car checks the operation of the driver's electric window motor (con­
trolled both manually and automatically) and the passenger's electric window motor (only controlled
manually).
Manual mode is the start-up and stopping of the window lift motor determined by the user manually by
prolonged pressure on the control buttons (period between 60 and 300 ms).
Automatic mode is the start-up of the window lift motor after a pulse (of over 300 ms) has been sup­
plied. The window will return to the rest position once the window has completed its travel. The win­
dow can nevertheless be stopped during this stage by again pressing one of the two buttons.
The driver's pushbutton unit is double, and so can control the passenger's window, only in manual
(with the ignition on).
The passenger's pushbutton unit is single and only carries out the manual function.
On the FASTBACK version, the driver's pushbutton unit has the rear window control always on manual.
It can also exclude the rear window pushbutton units (button A).
The pushbutton units on the rear doors work in the same way as the one on the front passenger side.
NOISE DETECTOR safety system
If the control switch is pressed when the window has reached the end-of-travel position, the electronic
control unit automatically cuts off the supply to the motor. This condition is recognized by an electronic
circuit called "NOISE DETECTOR", which can act by analysing the frequency of the disturbance gener­
ated by the motor brushes during rotation.
When the motor is turning it generates, by means of the commutation arising between the brushes and
commutator, a disturbance signal which is transmitted to the control unit via the supply line, and whose
frequency is proportional to the engine speed.
If the frequency of this signal exceeds 15 ± 5 Hz, the control unit recognizes that the motor is turning
freely.
When the window reaches the end-of-travel position or tends to jam for mechanical reasons, such as to
drastically reduce the normal speed of rotation, the frequency of the disturbance signal is reduced pro­
portionally. When this frequency falls below the specified threshold (15 ± 5 Hz), the NOISE DETEC­
TOR cuts off the supply.
Bravo-Brava
88 Publication no. 506.670/01