The turn signals stopped working on my R129 following winter storage. There is no tell-tale click or instrument cluster indication. Also, the hazard lights do not work. Based on other posts on this subject, I have replaced the fuses (they looked good but...), pulled the hazard switch and checked the contacts and diode, and even opened up the combination relay so that I can manually close each of the L/R turn signal internal relays. When I manually close the internal relay, the turn signals actuate for that side and the familiar click can be heard under the dash. They do not blink of course, as I'm actuating the relay.

Does anyone have the diagnostic steps necessary to narrow down the problem? I'm guessing that it is the combination relay, but I would like other opinions before I drop the ~$250 for a new one.

Thanks

Well Wayne, I would start by checking to see if your light bulbes are still there after winter storage. Then I would check for corosion or bad ground. Then I would suspect a faulty flasher or a bad switch at the steering column if you had that apart for any reason.

Hey Wayne, I was going to get back to you on this. You know how things go though. If you can wait, I'll try to get back to you Monday evening....Gilly

Thanks for the reply ejsharp, I checked all the bulbs and found them ok. They light up fine with the running lights on and when I manually close the internal relays. I suspect the flasher as well, but as I understand it, that's the hazard/combi relay which is fairly costly.

Gilly, I just returned from vaca and just getting back to the SL. I went as deep as I could without the diagnostics manuals. Waiting until Monday eve is fine. Let me know if there are any other items I should look at in order to provide you more information.

----
BTW, anyone know where you can find the engine and body&chassis diag manuals for a '90 R129?
----

Thanks again,

Wayne,

I think the flasher is the thing you hear click when you manually activate the relay. Not sure on the Mercedes. Have never worked on their turn signals. If so it means you are getting power to the flasher but the points are burnt and sticking together.

I'd forget about the whole "flasher" scenario, i don't believe it has on in a traditional sense. I think it's all controlled by the big relay Wayne mentioned, what is it Wayne, the combination relay? Or could be the exterior lamp failure relay. I"m sure it wouldn't be the first multi-function switch to fail, either, but I would think the hazards would probably still work if that was it......Gilly

Gilly, the relay I'm referring to is located in the center row front. In my MD CDs for a Model 124, it is called the combination relay (N10) for turn/hazard/etc. I know its different on the R129, but I don't have the docs :( PartsShop has it listed as the Hazard Relay for $243.

It is normally a sealed unit, but I carefully opened it to see what it contained. It there was 2 pc boards with a lot of electronics (chips, resistors, etc) and three coil type relays. One operated the drivers side turn signals and the other the passengers side. The third did not do anything that I could observe. It showed me that the circuits out to the lights, etc work fine. I also checked out the hazard switch and that checked fine. Continuity across switched legs and proper action of the internally diode (no leakback and ~38 ohms forward). So I think that leaves be somewhere in the middle... at the hazard relay???

Gilly,

The thing that puzzles me is that Wayne implies that he hears a single click at a location separate from the relay. To me that click implies a flasher unit downstream from the combo relay.

The MB PN for the Hazard Relay is 129.820.10.26 and the designations for the internal coil relays within are R11 and R12 for the R/L turn signals and R13 for ???. It seems like R11 and R12 circuts are connected by a 21 pin connector and R13 is via a 6 pin connector.

I guess I'll just reserve any more comment until I get a chance to review the wiring schematic, except I still believe that one critical component that is being overlooked is the exterior lamp failure module. Everything runs through it on a 129 EXCEPT the center stoplamp, that is a dedicated circuit from the brakelight switch, and possibly the headlamps don't run through it...Gilly

OK, Wayne, here's some work for you. First of course, the fuses. These are both in the main fuse box by the brake booster. Fuse 9, powers up the Combination relay module. The power input from there is socket 7 at the realy module, hot with key "on". Fuse 9 also supplies power to the hazard switch for the signal to the relay module for hazards "on". Fuse 6 provides power to the turn signal switch for signalling turns, so check that one, too. `OK, heres some info direct from the ETM, this all pertains to connector 2 (the larger connector on the relay module:
Connector 2, socket 3 Main ground to W1 (ground behind cluster)
socket 6 Right turn signal input from signal switch (should be 12V with key on and signal in right turn position
socket 7 power from fuse 9
socket 9 Hazard flasher control lamp signal (output) 12V with exterior lamps "on"
socket 10 hazard flasher signal input (with hazard switch "on" 12V
socket 12 left turn signal input (see socket 6 above)
socket 15 left turn signal output (self explanatory)
socket 19 right turn signal output " " " " "
The outputs at 15 and 19 are both for the lamp units and the instrument cluster.The lamp monitor is only controlling the park lamp outputs in this area of the system, I know it is actually controlling more than is shown here, but not the turn signals. Many of the pins on the relay module are note noted in this diagram. The relay module has control over the turn signals, rear window defroster (on the hardtop) wiper motor, and anti-theft alarm. Hope this helps you out, let me know if you need any more help, and also let me know how it's going.......Gilly

Gilly, thanks for the direction on the turn signal problem (no pun intended). I will check these feeds out per your instruction and post the results, probably tomorrow.

-off topic: I'm considering digging in and replacing the head gasket on this M104. It has the typical leaks on the passangers side front and rear, but no oil in the coolant... yet. I have an MB book on order which details the M104 engine and that I will use for direction. Have you done one of these before (probably many), and if so what is your take on the complexities of the job for an experienced DIY'r?

Thanks,

Try cycling the hazard switch on/off a few times, then try the blinkers. Cycling the hazard switch seems to cure many of the turn indicator failures on the older cars, might do the same on the 129.

Mike, I read the posts on the hazard switch and was hoping that was the case. Unfortunately no luck.
Thanks,

Test Results
 

Gilly, below please find the results of the ETM test:

true - socket 6 Right turn signal input from signal switch (should be 12V with key on and signal in right turn position
true - socket 7 power from fuse 9
false - socket 9 Hazard flasher control lamp signal (output) 12V with exterior lamps "on"
true - socket 10 hazard flasher signal input (with hazard switch "on" 12V
true - socket 12 left turn signal input (see socket 6 above)
false - socket 15 left turn signal output (self explanatory)
false - socket 19 right turn signal output " " " " "

Based on the fact that all inputs are true and all outputs are false, is it correct to say that the relay module is bad?

You mentioned that this module also controls the wiper motor (along with other things), but the wiper still runs with the relay module removed!

Also, please see my earlier post in this thread about the head gasket. Oh fun...!

Thanks,