Confused about headlight switch, mainly the foglights - W164 ML350

[matsquatch]

Hi there, hope someone can offer some advice - I have inherited my late Father's W164 ML350, which while a bit neglected, seems to be ok in general, however I am puzzled about the lights.

There have been a few issues with the car, it was laid up in a barn for a year, and had a mouse in, which thankfully doesn't seem to have chewed anything important, but I guess there is a lot of wiring! The battery was completely dead, so I had a very entertaining hour swapping the underseat battery (why Mercedes, why??) and did the aux battery while I was there. I've read things about needing to reset the car after a battery swap, but nothing definitive. I also found the boot was damp, so read up on that and found the rear high level brake light was basically disintegrating and letting water in - I'm waiting for a replacement so some gorilla tape is keeping the damp out at the min. I've some replacement back light gaskets too, in case the ones on turn out to be leaky.

But I digress - the car seems to have self levelling xenon headlights, what look like running lights directly under the main lights, (scratch that, they're the indicators!) and a thin looking strip on the lower bumper of what I assumed were front fog lights. I was a bit grossed out by the stickiness of the headlight switch, so thought I'd try and remove it to clean it, but noticed that there was no front foglight light. And the switch only pulls out one notch, which sure enough turns the rear foglight on. I came across a spare switch from a neighbour, which looks identical, but has a extra notch (so 2) and a front foglight light. The parts codes are (obviously) different (A1645453704 for the original, A1645450504 for the replacement), but I can't really understand what's going on with the lights at the front. Curiosity got the better of me and I extracted the original switch (which was a battle in itself) and the pins are identical (5 pins in, 9 empty). When I push the notch in to turn the foglight off, there is an increase in the front light for a second, which them dims (but is on). The "running lights" have been activated in the settings menu, so when the switch is in the off position, the side lights stay on, which I assume is correct? I hope it's not wiring, the little brown lodger lived in the back, so fingers crossed it's something else......

I guess there's a lot to go at there, and I'm happy to clarify anything I can (with pictures), but any direction people could point me in would be welcome! Thanks in advance!

Matt

 

[AltonAnt]

I’m not sure if yours is the same but I think on mine (I don’t use them that often) the double detent option is only possible on full where the single is on dipped.

Do you have the handbook?

BTW - the stickiness is likely the rubberised paint breaking down and cannot really be cleaned. Either remove it or it sounds like the assembly may need to be replaced anyway.

 

[Jkh112]

of the stickiness is the rubbery coating disintegrating then it can be cleaned with isopropyl alcohol.

 

[matsquatch]

I’m not sure if yours is the same but I think on mine (I don’t use them that often) the double detent option is only possible on full where the single is on dipped.

Do you have the handbook?

BTW - the stickiness is likely the rubberised paint breaking down and cannot really be cleaned. Either remove it or it sounds like the assembly may need to be replaced anyway.

Hi, thanks for the reply - on the original switch, there is only one detent, it's either in or out, but you're right, you have to have it on the dipped beam setting. On the replacement one, there are two detents, but also and extra light to show that the fronts and/or back are lit. Even with this switch installed, it doesn't change the behaviour of the lights. I do have the manual, but it seems to be fairly generic when it comes to the lights, it covers a multitude of options. I guess it's entirely plausible that the little thin lights at the lower bumper just aren't fog lights!