Faulty DRLs? How to fix the DRL controllers on the cheap!!
 

A week or so ago, the wife's Q5 Right DRL went dead. She has also been having an issue with the AC blower so I figured I'd spend the day and check it out.

First off, I stripped the whole headlight out of the car as the DRL controller sits inside the headlight. This, my friends, was not an easy undertaking as it's the bumper and various bits, brackets, manifolds and another million things to strip off. But yay, I had the headlight out eventually.

Imagine my surprise when I realised I could've just removed the one back cover, unscrew two bolts and the controller would come out. Easy Peasy. Today was going to be one of those days...

So, while I sit and have a smoke, I read up about the DRL's and, surprise surprise, this is another one of those issues with '09 and '10 Audi's - the DRL modules are a real problem. This seems to be for all cars, not just the Q5's. Looking at pricing I was going to pay over R5k for a module from the agents. And with the car now 4 months out of plan, I doubt Audi will entertain any goodwill gestures, even though they know it's a problem.

I then opened the unit up to have a look if it's at all serviceable and it looked like the kind of thing I can fix, being an electronics guy. In order to make my life easier, I remove the other DRL as well so that I can compare the two on my bench when fault finding. And guess what, the other side has already been replaced :) I know this because it was only held on with one screw (not two like it should be) and it had a 'B' suffix after the part code.

Here we go with the two units next to each other, new one on the left.
Attachment 23989

I believe that the revised module had a fix applied to it in order to make it more reliable. Well, to be honest, they only made one fix and that was changing one diode to a larger one. See below, with the only change made between the boards marked with a black circle.

Attachment 23990
And
Attachment 23991

I didn't even bother doing any further fault finding, I simply powered the faulty one up on the bench and sure enough, the SOT23 diode was blown. I'd hazard a guess that this diode is rated for around a 1A and the new one for 3A. I didn't have any 3A diodes in my bin and with some testing on the new module I determine there's nothing fancy about the new diode (it's not a Shottky type), it's just a plain general purpose 3A power diode. I had a handful of 1N4007's here, that are rated for only 1A but I connected two in parallel in order to improve power handling. There's nothing further down the chain that needs more power than that so I just went with it. If it does break again (which I seriously doubt) then I'll get the correct type.

Anyway, here's the fix applied. I didn't remove the faulty diode as it simply went open circuit so wouldn't interfere with the fix. These modules are so covered in conformal coating, trying to remove the old diode would just make a mess.

Attachment 23992

After the repair, I quickly connected the Right headlight again to test and, Voila!

Attachment 23993

Now the nightmare of assembling the whole car again, but getting it fixed for the princely sum of two 50c diodes made it worth it :)