Fault diagnosis

The CLOCK SPRING is a part connected to the stalk unit. It allows the steering wheel to turn while ensuring electrical continuity between the driver's side air bag module and its wiring.

The clock spring consists of a container with three leads emerging from it. One lead is connected to electrical wires from the control unit while the other two leads are turned toward the car interior, where they are connected to the horn and the air bag module.
Inside the two plates, the module and horn button connection leads are wound up into a coil so that they can follow steering wheel movements.
The clock spring is fitted with a device which automatically prevents it from turning when the steering wheel is removed. This action prevents the upper plate, now no longer secured to the steering wheel, from turning freely to wind up or unwind the leads and lead to the possibility of breakage.

When the steering wheel is fitted, the device is automatically released.

When removing-refitting the clock spring, ensure that the spring is refitted in its original position.

If for some reason the upper plate of the clock spring turns in relation to the lower plate so that the position upon removal can no longer be determined, it is absolutely necessary to replace the clock spring.

If replacement is required, the clock spring is supplied together with the stalk unit. THE UNIT MUST BE INSTALLED WITH THE WHEELS ALIGNED WITH THE VEHICLE'S LONGITUDINAL AXIS (STRAIGHT AHEAD), because this is the corresponding position of a new part. A new device is fitted with an safety key which keeps it locked. This key must be removed when the steering wheel is installed to allow the system to turn correctly.

FAULT DIAGNOSIS

While the vehicle is in motion, the electronic control unit automatically monitors the air bag system and stores any faults. When a fault is detected, the unit stores it and turns on the air bag warning light on the instrument panel.The warning light comes on for about 4 seconds (initial test stage) upon start up and then goes off. If the warning light does NOT come on or does NOT go off after 4 seconds, the air bag system must be faulty. System activations following crashes of particular severity are also stored in the control unit.

Diagnosis using a Fiat/Lancia Tester

Faults stored in the control unit can be analysed using a FIAT/LANCIA TESTER or other diagnostic tool. Anomalies stored in the control unit may be deleted once the fault has been repaired using a FIAT/LANCIA TESTER or another diagnostic tool.

NOTE If a crash causes the system to be activated, the control unit memory cannot be deleted and the unit must be replaced in all cases. The control panel warning light also stays on permanently.

If module lines need to be tested for breaks during fault diagnosis, the modules must be disconnected from the wiring and replaced with appropriate dummy resistances.