MFSW and horn stopped working. AlteaXL 2.0 TDI 2008

[SIMC]

Hi

I have a Seat AlteaXL 2.0 TDI 2008 with MFSW.
4 buttons on each side for radio control.

Suddenly the buttons and horn stopped working. No light in buttons, no reaction when pressing the buttons and no horn.

VCDS gives me this:

Address 16: Steering wheel Labels: 1K0-953-549-MY8.lbl
Part No SW: 1K0 953 549 AQ HW: 1K0 953 549 AQ
Component: J0527 636 0070
Coding: 0002042
Shop #: WSC 04941 785 00200
VCID: 01024FE7589F1E306C-8054

1 Fault Found:
01426 - Controls in Steering Wheel (E221)
004 - No Signal/Communication


I removed airbag and inspected the buttons, but the only thing I got was the part no on the buttons (5P0 959 537)
Anyone knows this failure? Is it the buttons (5P0 959 537) or Steering wheel electronic module (1K0 953 549 AQ) that has failed? Or something else?

Please advice.

[Flash2]

Welcome to the forum.

Your fault might be caused by a break in the clockspring / slip ring behind the steering wheel. The control unit for MFSW (built into the wheel) & the horn share wiring through the clockspring.

Jim.

[SIMC]

I tried an ohm tester, and tested the slip ring. All 8 wires map trough, no short and no breaks.
I have also tried to connect the buttons (5P0 959 537) directly to the Steering wheel electronic module (1K0 953 549 AQ), without the slip ring. And that didn't bring any life to the buttons :-(

Is there any way to test the 2 modules? Or is it just to replace one part at a time until it works? Sound really expensive unless I make it the first time....

[Flash2]

Sorry I've not got back to you sooner. Are you any further forward with your steering wheel controls?

I was thinking that since the buttons aren't lighting up, perhaps the supply or ground is missing from the button control unit. Have you checked that?
Check for voltage across pins 1 & 2 of the five pin connector on the button control unit on the steering wheel. The ground is on Pin 1 (blue wire) & the supply is on Pin 2 (brown wire).

Jim.

[SIMC]

Hi. Thanks for your reply

I have just testet voltage of pin 1 and 2 (orange and blue).
And there is 11.61v when buttons are NOT connected
And 0.48v when the buttons are connected.

I my case I have the following colours:
1 Orange (I guess this is Ground)
2 Brown (LIN) What is LIN?
3 Blue (I guess this is supply)
4 Grey (Horn)

On the drawing, the buttons are "A27mf" and the Steering wheel electronic module is "A23"
IMG_1821.jpg

[Flash2]

If you have 12V (OK, 11.61V) when the button controller is disconnected and only 0.5V when it's connected that suggests there is a high resistance on either the power supply or the ground to the button controller (A27mf).

Next, you will want to carry out a couple of voltage drop tests to identify where the resistance is :

connect your black voltmeter lead to the vehicle body (ground) and the red lead to the orange wire at the controller. With A27mf connected, the voltage should be less than 0.5V. If it's higher, the resistance is on the ground side of the circuit.
If the voltage in that test is correct, then connect the red meter lead to a known good 12V supply (maybe an unused fuse connection on the fusebox) and the black lead to the blue wire at the controller. Again, the voltage should be less than 0.5V. If it's higher than that, the resistance is in the controller supply wiring.

LIN is a data bus wire.

Jim.