Inside the Rotary Coupler
The object of this page is to try and persuade you NOT to try and repair your steering column rotary coupler should it fail.
The coupler forms part of the SRS Airbag Circuit, and unless you have the means to fully test the coupler after having taken it apart and tried to repair it, I seriously do NOT recommend re-installing it back in the car.
The coupler can be removed from the steering column after having first removed the SRS airbag. (see Horn Failure ).
NOTE: Before carrying out any electrical examination of the horns, SRS , or steering column, DISCONNECT THE BATTERY AND LEAVE FOR AT LEAST 10 MINUTES FOR THE SRS AIRBAG SYSTEM TO DISCHARGE.
Remember too that disconnecting the battery will mean your radio will loose it's security code and will have to be re-entered.
The coupler body basically comes in two halves, the lower section firmly fixed to the steering column and the upper half fixed to the steering wheel, and therefore capable of rotating. Before removing it from the steering column it is important to ensure that the alignment of the two halves is 'dead center'. This is indicated by a small white mark on the top face of a geared toggle mechanism on the top face of the coupler. Each full rotation of the steering wheel rotates the white mark by one tooth of the gear, thereby moving the white mark off centre. If you centralise the steering wheel, ensuring the front wheels point straight foreward, the white mark should be flush with the top face of the coupler.
Having removed the airbag and steering wheel, it is critical to maintain the rotary alignment of the two halves of the coupler, assuming that you are going to replace
it in the vehicle. The best way is to stick a length of tape across and down the sides of the coupler to stop the top half rotating.
The coupler itself is capable of rotating through approximately 4 ½ revolutions, but the operating region is in the central 3 full revolutions of the total movement.
The two halves of the coupler are held together by a central ring that has 4 integral clips. With a small screwdriver it is possible to lever these clips inwards and jam them with paperclips. Once all 4 are held back, the two halves can be split apart.
There is a small toggled gear mechanism, it's central position highlighted with a white spot. This should be flush with the top face of the coupler when the steering wheel and drive wheels are aligned in the forward position. For every rotation of the coupler through 360 degrees, the
gear gets toggled one tooth by a small pip on the inside lower face of the coupler, such that the white spot will no longer be flush with the top face.
Inside there is a flexible cable or FPC (flexible printed circuit) that provides the electrical connection. The FPC is permanently fixed at either end, but runs through a gap in a rotating cable tensioner, thus changing direction and allowing for the full rotation of the circuit.
The fact that it changes direction makes the FPC susceptible to failure, but to replace it, assuming that you can acquire the correct cable part, means that you have undo and then remake the fixed connections at either end of the FPC.
The danger in repairing this yourself is that you may not be able to make a 'good' connection with the FPC at either end, resulting in failure to trigger the SRS airbag when you need it, or tripping it immediately you reconnect the battery!
The coupler body basically comes in two halves, the lower section firmly fixed to the steering column and the upper half fixed to the steering wheel, and therefore capable of rotating. Before removing it from the steering column it is important to ensure that the alignment of the two halves is 'dead center'. This is indicated by a small white mark on the top face of a geared toggle mechanism on the top face of the coupler. Each full rotation of the steering wheel rotates the white mark by one tooth of the gear, thereby moving the white mark off centre. If you centralise the steering wheel, ensuring the front wheels point straight foreward, the white mark should be flush with the top face of the coupler.
The two halves of the coupler are held together by a central ring that has 4 integral clips. With a small screwdriver it is possible to lever these clips inwards and jam them with paperclips. Once all 4 are held back, the two halves can be split apart.
There is a small toggled gear mechanism, it's central position highlighted with a white spot. This should be flush with the top face of the coupler when the steering wheel and drive wheels are aligned in the forward position. For every rotation of the coupler through 360 degrees, the
gear gets toggled one tooth by a small pip on the inside lower face of the coupler, such that the white spot will no longer be flush with the top face.
Inside there is a flexible cable or FPC (flexible printed circuit) that provides the electrical connection. The FPC is permanently fixed at either end, but runs through a gap in a rotating cable tensioner, thus changing direction and allowing for the full rotation of the circuit.
The danger in repairing this yourself is that you may not be able to make a 'good' connection with the FPC at either end, resulting in failure to trigger the SRS airbag when you need it, or tripping it immediately you reconnect the battery!