Instrument Cluster lights intermittent

[simon84]

Hi,

on my 2004_09 X5 3.0d the instrument cluster lighting is intermittent.

Banging on the top of the panel usually brings it back on (when off) or off (when on).

All Internal LED lights are affected (also on the right side of the dash/airco controls etc, not only cluster itself).

I have already checked:

Instrument cluster itself:
Completely dismantled, checked electronics for signs of cracks/bad solder joints etc., used contact spray on all connections. Had the naked instrument cluster board connected and reproduced problem, banging on the dash itself , same behavior, even with KI hanging in the air completely decoupled from any "banging" effects

Did the same with the LCM module itself as well. When the problem occurs, a whirring can be heard in the LCM, as soon as I hit the dash and the lighting comes on, the LCM whirring goes away. Knocking/Tapping/Hitting the LCM itself or pulling on the wires does no change.

So it appears the LCM isnt at fault either.

Did same procedure with the board computer monitor /MKIV screen as well. Nothing to be found.

I had the impression when hitting the dash on the passenger side less force is required to make the lighting go on/off.

Any ideas ? Could it be that there is one LED which is short to ground intermittently ? How are they dimmed e.g. which component is doing the dimming? Dimming LED must somehow work by pulsing them, I dont think you can just dim LED with a resistor right ?

I checked the Dimmer in DIS and it shows 4V on lowest position and 0V on highest, so seems to be working as expected.

None of the modules (KI/LCM/Rain Sensor etc.) show any relevant errors when reading out with original BMW DIS system.

Does anyone know how the wiring runs under the dash? The fact that I can just hit the dash over and over again to make the lighting go on/off kind of makes me think its either a bad solder joint in another module I havent looked at yet, a bad wire/connection or a bad ground point somewhere....

Any input greatly appreciated

Cheers,

Simon