w210 Turn Signal / Combination Switch failures?
 

Hey guys, I've got a question about the different failure modes for a turn signal / combination switch on my w210.

Instead of just one function failing, mine is failing to operate on ALL functions. No turn signals, no high beams, no wiper functions. This seems odd, as every other thread about combo switches shows one or another function failing - not ALL of them.

Before I start throwing parts at it, has anyone ever experienced a complete failure before? Or heard of it? I'd hate to put a new one in only to find it's some other weird esoteric problem, like maybe a CanBus issue. Any help would be sincerely appreciated!

Thanks in advance!

Combination switch on a 210 works with the EIS (ignition key) switch.

When you select the various modes it switches resistors onto control lines. The EIS reads these resistances and generates the CAN bus messages to the various controllers.

Wipers, horn -> front SAM
turn signals, flash the brights -> headlight switch
Cruise -> hard wired to the ECU

The 140 was the first car with CAN bus. 210 was the first mainstream car with it and they were still tinkering with the best ways to do things. By the 211 time they had a 'steering wheel control' module that integrated everything on the column and put it on the CAN bus directly.

If you have access to a Xentry you can get into the system through the 38 pin plug and see what requests from the combination switch are being received by the EIS when you move the combination switch.

jay_bob, That is extremely helpful information - thank you SO much for that!

Now it seems less likely it's the switch itself. Perhaps it could be a problem with the power source or ground path for the switch, thereby killing ALL functions. Or it could be a bad com line. IDK. I wish I had a wiring diagram, but I'm flying blind.

I don't have access to a Star / Xentry unit. Ironically enough, just last week I was delving (again) into the research needed before buying one. There are so many different versions and vendors, and finding a reliable mux seems to be an issue. C3 or C4? I'd need the HHT functions too, so that rules out a C5. (I think.) I'll post a separate question about that in the Tech Support section.

I guess it's time for me to cough up the big bucks and sell off my "old red brick" Snap On scanner...

Thanks again!

Get a C3. It supports the 38 pin plug and the newer models as well.

From your sig you have 4 W210s and 3 W124s. The C3 will support the W124s also, there is a cable with banana plugs that you stick into the right ports on the diagnostic connector. I think the 500E has a 38 pin but it is different than the one on the 140/210 from what I have read.

The package I got has 4 vehicle cables:
- OBDII for W211 and newer
- 38 pin for the W140 and W210
- Banana plugs for the W124/later W126 with the diagnostic port
- SAE connector for heavy trucks, never took this one out of the plastic...there are menu choices on Xentry for the Mercedes tractor trailers/motor coaches that are in the rest of the world.