Rear diff switch not engaging lock

[caddykid88]

I've just replaced all the bulbs on the rear diff switch and I soldered in two bulbs that were not working which lit up the transmition and the green light. All the bulbs work now, but when I engage the diff switch nothing happens now, the green light does not come on. It worked last winter which is when I last used diff lock. Does anybody have any idea what I can do or test or replace to get it working again? Honestly though you fix one thing and something else needs fixing. very frustrating

[CoupeWannabeS2]

I think the circuit board in the diff switch can be damaged with heat. Did you test it worked immediately before taking the soldering iron to it.?

From memory if you get your rear bench seat out, you should be able to hear the engaging / disengaging in the actuator (right word?) when you push the switch working.

[UrS4boy]

Rear Differential Lock 101

This might have your answer (unless you fried your circuit board when replacing the bulbs).

Rear Diff Lock 101: http://forums.quattroworld.com/s4s6/msgs/170940.phtml

[caddykid88]

Ok that's great thanks, plenty of info to get through. I will have a closer look when I can get the car on a ramp.