Seat Belt Tensioner: Testing and Inspection
Belt Tensioner Testing on Vehicles WITHOUT Airbag: For vehicles with Airbag, [1][2]Component Tests and General Diagnostics
Special Tool:
Testers:
Digital pocket multimeter e.g. Hermann Avometer 2003
e.g. Fluke, 23
Multimeter e.g. Sun, DMM-5
The following tests for triggering or function must be performed:
a) Following an accident with visible deformation to:
- the guide rail.
- the belt retractor.
- the belt buckle.
b) After removing a belt tensioner.
c) After installing optional equipment requested by the customer, which may influence the function of the belt tensioner system either mechanically or electrically.
This test program is divided into:
A. Mechanical function
B. Electrical function
A. Mechanical Function:
Testing the belt tensioners for triggering (center pillar covering or belt tensioner removed).
Type 1
Cable Tensioner (1st version, 2nd version), Check whether the colored mark on the cable (green or yellow) is still visible. If the colored mark is still visible, the belt tensioner has not been triggered. If no colored mark can be seen, the belt tensioner has been triggered and must be renewed.
When the series was introduced, some vehicles were built with no colored mark on the cable of the belt tensioner. These must be tested as follows:
- Remove protective rubber cap on end of tube and measure distance "X". To do this, insert a round implement or screwdriver of approx. 10 mm diameter and measure the depth.
Model Distance "X"
107 140 mm ± 5 mm
123 140 mm ± 5 mm
126 170 mm ± 5 mm
If the measured distance is shorter than the distance given above, the belt tensioner has been triggered and must be renewed.
Type 2
As of 01/86, there is an observation window in the housing of the belt tensioner, through which the cable is visible. This means that it is no longer necessary to remove the belt tensioner for the test. Belt tensioners where no cable is visible have been triggered and must be renewed.
Type 3
As of 08/87 belt tensioners are supplied by two manufacturers.
The housings of belt tensioners supplied by REPA, like type 2 housings, incorporate an inspection window, through which the wire cable can be seen. If no wirew cable can be seen, the belt tensioner has been actuated and must be replaced.
Type 3 belt tensioner is distinguished by an approx. 80 mm shorter tube.
The housings of belt tensioners supplied by AUTOFLUG also incorporate an inspection window, through which 2 wire cables can be seen. If only 1 wire cable or no wire cable at all can be seen in an AUTOFLUG belt tensioner housing, the tensioner has been activated/triggered must be replaced.
B. Electrical Function:
Belt Tensioner Wiring Diagram:
N2/1 Control unit, belt tensioner
R12/1 Detonator, belt tensioner, front left
R12/2 Detonator. belt tensioner, front right
X28/1 Plug connection, power supply, belt tensioner
X29 Test coupling, belt tensioner
W12 Main ground point, center console
a To fuse box, terminal 15 R
Testing the Triggering Circuit of the Detonators:
1. Disconnect negative terminal of battery and cover.
2. Connect multimeter to the 4-pin test coupling (X29) (2 pins used).
NOTE: The test coupling (X29) is connected in parallel with the detonators.
Location of 10-Pin Plug Connection or the 4-Pin Belt Tensioner Test Coupling in the Vehicle:
Model 107 (1st Version up to 4/87) - On Parking Brake Bracket:
Model 107 (2nd Version as of 4/87) - On Panel Under Pass. Foot Rest:
Model 123 (With Air Bag) - Under Driver's Footrest:
Model 123 With Belt Tensioner - Under Driver's Seat:
Testing:
NOTE: If the vehicle is severely damaged, the control unit (N2/1) on the transmission tunnel must be checked for visible deformation or damage to the housing. Control units with damaged housings must be renewed.