Repair your headlight switch illumination

[toff]

Hi,

Since I bought my B6, the headlamp switch cluster has failed to illuminate at night (only the fog lamp symbols & the central knob were illuminated).

I decided to take it apart and see if I could fix the problem. It turned out that the top two LEDs are wired in series.. so whilst only one of them had blown, it was preventing the second one from working.


1. Take your headlamp switch cluster out of the car - press the knob in and turn to the right, then pull the switch cluster towards you to get it out.

2. Bring the lamp cluster inside and dismantle it. Hopefully the photo below will give you an idea of which parts are supposed to separate:



Once you've un-clipped the front shroud from the back part (with the connectors on it) you can then gently rotate the switch knob and it will separate from the back part.

The circuit board pulls away from the back part (it's a clever little design, the wires just pop-out of the metal receptacles).


3. Using a 12v power supply (from digital picture frame!) and some crocodile clips, I hooked-up the power to the contacts to illuminate the bulbs. Sure enough, only a few of the LEDs light-up.



Note: I just used trial & error to find which contacts to connect the power to! I blew one of the central LEDs in the process - make sure you use the right contacts as indicated above (the red lead is positive, the white lead is negative).


4. Using a 5v LED that I had in my electronics kit, I pressed the legs against the solder points of the broken LEDs - it didn't light-up.

Most LEDs are polarised, so I reversed the legs and sure enough, the LED light-up AND the other LED light-up too, indicating that the LEDs were wired in series (the anode[-] of one feeds onto the cathode[+] of the other).

You can see in the photo below, I temporarily attached the legs of the replacement LED and suddenly the circuit is complete and everything lights-up (apart from the broken LED obviously).




5. At this point, I noted down the polarity (which way round) the LEDs needed to be soldered in by colouring the Cathode[+] with a permanent marker.
I then de-soldered the broken LED and the LED next to it (just to ensure both LEDs were of the same type / brightness) and replaced them with my new LEDs. I also replaced the central LED I blew-up earlier when finding out which contacts were +/-

The Photos below show the back of the circuit board (before replacing the LEDs) and the front with the replacement LEDs soldered in! It's important to re-attach the power for a quick test before you re-assemble the switch!





6. Simply re-assemble the lightswitch cluster in reverse order and you're ready to stick it back in the car!

My Blackberry was unable to take a very good photo, but the illumination was pretty much back to normal!



If you've found the above useful, please show your appreciation by clicking on the button in the bottom-right hand corner of this post.

Al.

[kite]

I have a LED that blinks on my switch, I suspect its failing.
In the past I've managedto get the switch apart but couldn't see how to remove the PCB,
Could you explain in a bit more detail.
I'm not very handy with an iron and its a shame your not closer to repair mine for a few beer tokens....

[mrmule]

Perfect thread matey...

[MFGF]

Very impressive! You're a brave and talented man Al!

[defsix]

Should the little white knob on the switch glow red too ?

[toff]

I have a LED that blinks on my switch, I suspect its failing.
In the past I've managedto get the switch apart but couldn't see how to remove the PCB,
Could you explain in a bit more detail.
I'm not very handy with an iron and its a shame your not closer to repair mine for a few beer tokens....

When I was experimenting, touching the [+] power on differnet contacts, the central LEDs started flashing.

I don't know what it means exactly but I suspect that it's when a short is detected on the circuit somewhere.. not necessarily in the headlamp switch but in the car's lighting wiring loom! Have you walked round your car whilst all the lights are on to see if anything isn't working?

With regards to removing the PCB - what stage did you get upto? Did you manage to seperate the front bit (containing the switch) from the back bit (with the connectors on it)? If so and you could see the PCB with the metal clips poking through it, you simply need to pull the PCB away from the back part (the rigid wires pop-out of the metal receptecals).

Let me know and I'll try to help... (I only thought about doing the how-to guide after I'd taken it all apart!)

Should the little white knob on the switch glow red too ?

Yes, the two central LEDs on the circuit board are designed to illuminate the red dot and the bulb symbol on the switch - they should be illuminated whenever the key is in the ignition.

I am happy to solder-in new bulbs for people if you send me your PCBs (or your whole headlamp switch if you can do without it for a few days!)

Al.

[kite]

I have managed to get the switch apart in the past, down to where I can see the PCB I have had the courage to just pull the PCB off.
Would the switch work OK if I was to send you the PCB and put the switch back together.

[fourringsrus]

Toff, that was a great HOW TO and though I currently have no problem with my switchgear I felt compelled to praise you for putting the thread together and say how good it is to see someone prepared to have a go
So please collect your rep click on the way out
Stuart
oops I rep'd kite by accident but hey ,he's a good guy too

[kite]

Thanks for the "click", have one back.......

[toff]

LOL - you guys are clicker-happy!

Cheers fourringsrus and everybody else who "thanked" - it's a pleasure to do the write-ups knowing they help the community & are appreciated.

Kite: I think the switch would work without the PCB - I believe it's just for illumination and to indicate when the fog lights are on. All of the switching is done in the back part.. but you'll have to try it to find out for sure.

The only reason to send it to me would be to replace LEDs that have broken.. I'm only amateur at electronics...
I can't troubleshoot your flashing light.. as aforementioned; I believe that indicates a short circuit or reverse of polarity somewhere on the lighting circuit.

That said, I could put your circuit into my switch and I can tell you if it then functions properly. Click on my name (next to my TDI Quattro avatar) to send me an email and I'll reply with details of where to send it etc.

Al.