Problem: A whole group of buttons aren't lighting up as they should.
Models: All E32 and E34 models with the IHKA climate control system.
Fixing the illumination:
The section "Climate control illumination" already shows how to remove and disassemble the control panel. So I won't repeat those steps here.
The LEDs for the buttons are grouped in series of three. If one breaks all three will remain dead. To find out which one was broken I powered the PCBA by soldering some wires to the GND of the bulb and the lights on signal on the blue plug of the panel. This lighted 2/3 of the panel up. If you don't have a power supply in your house you should be able to power the panel up in the car by reconnecting the blue plug.
To find the deffective one I shorted the terminals of the LED on the back one by one to see which one was broken. After shorting the first LED the other two LEDs lit up like a christmans tree. Easy enough!
As this is a newer planel then the one that was installed in my 735i the buttons are clipped to the PCBA. So I I first had to remove the buttons to I could access the LED. This is done by carefully uncliping the plastic clips on the four corners. And by careful I mean careful. The plastic in the clips won't be as flexible as it was 15 years ago when it was assmbled.
Be sure to catch the springs while raising the buttons. In my case the came flying out before the LEDs where exposed.
I desoldered the LED with my tin sucker. Personally I like using desoldering braid better, but since I was out the tin sucker had to do.
As LED are diodes the orientation is very important. So make sure the annode (long leg of the LED) is on the side of the blue connector.
Time to solder the new LED
And try it out to see how a fully lit panel should look:
Total amount of parts and cost: LEDs are cheap so the repair was practically free! I do like those prices!
Total amount of time: Nice job to do on your lunch brake.
Story by Johan.
If you would like to add any comments, remarks and/or corrections to this procedure, feel free to email Mike Oswald and we'll put it on our site. Share your experiences with us so others may benefit from it.