Seat Belt Tensioner: Description and Operation

The cable tensioner (2nd version) is a further development of the turbine tensioner and has been installed since 09/84.

Method of Operation:
The complete unit is installed in the left-hand and right-hand center pillars and connected electrically by means of a 2-pin plug. The belt tensioner unit is automatically shorted by means of a short-circuiting link before assembly in the vehicle. The short-circuiting link is automatically opened when the plug connection is plugged in. If the control unit sends an electrical pulse to the propellant capsule, high-pressure combustion gas is released. This propellant gas passes by way of a T-piece to the plunger which is accelerated upwards. The wire cable pulls on the cable pulley and rotates it, and thus the belt retractor, to tension the seat belt. This reduces any slack in the belt and prevents the so-called film-reel effect in the wound belt.

Test for Triggering:





A colored mark (green or yellow) is present on the cable to check whether the belt tensioner has been triggered. If no colored mark is visible, the belt tensioner has been triggered and must be renewed. During the launch of this series, several vehicles were manufactured without this colored mark on the cable of the belt tensioner. These belts must be tested as follows:





Remove the protective rubber cap on the end of the tube and measure dimension "X".

Dimension X (124 Chassis): 170 ± 5 mm

If dimension "X, is less than the specified length, the belt tensioner has been triggered and must be renewed.

As of 01/86, there is an observation window in the housing of the belt tensioner, through which the cable is visible. Belt tensioners where no cable is visible have been triggered and must be renewed.





As of 08/87, belt tensioners are supplied by two manufacturers.





The housing of the Autoflug belt tensioner is also fitted with an observation window through which 2 cables are visible. Autoflug belt tensioners where only 1 cable or no cable is visible, have been triggered and must be renewed. The Autoflug belt tensioners are factory-fitted with a tube which is approx. 80 mm shorter than that of the Repa belt tensioners.

Repa belt tensioners also feature these shorter tubes as of 01/88.