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.

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

Wayne: I haven't had a fusebox apart on one of these lately. One thing to note is all of your "false" readings are outputs. You won't have any outputs without the relay in place, so I believe you need to get the larger of the 2 connectors out of the fusebox and plug it in, then test the outputs with the appropriate actions taken on the left and right directional and the hazard switch from the bottom of the connector. I'd say it's a safe bet that if the inputs, powers and ground are there that your looking at the combo relay as the fault, as it sure seems like you won't find any power at these 3 outputs from the relay. As far as why your wipers work with the combo relay removed, that stumps me. You have the relay completly "it's in my hand" removed? I am just stating what is says in the ETM. They have the function of the combo relay broken down into several diagrams, I just copied the one for turn/hazard lights. I should look and see if there is some fail-safe for the wiper motor that enables it to work in the event of a defective combo relay, kinda like the center stoplight working direct from the brakelight switch in case the lamp monitor module takes a dump. I'm curious, if the wipers work with the combo relay completely pulled, do the wiper function normally, that is, intermittent, slow speed, high speed, all work? I'm thinking it's possible the wipers are on the smaller connector to the combo relay....Gilly

Gilly,

I did have the relay plugged in when testing the outputs. So I guess I will go for the new relay. The wiper did appear to work normally when the relay was "in hand". Interesting...

ps: what are your thoughts on the head gasket question?

Quote "-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,

Wayne: I think you could probably handle a 104 headgasket. Wait till you get the book. The special tools involved-well, I can't really think of anything really. A cherry picker will help (oh, that's area slang for a engine hoist) that damn head is heavy. I don't think yu need to worry about oil/coolant mixing on a 104, that's mostly 102 and 103 problem. With the 104, it's just external leakage. I didn't get a chance to look at the wiper wiring today. We got a new guy who is working out good, but we're getting into the spring rush, so we still can't hardly keep up. Got a sweet job to do tomorrow night (time and a half after hours pay), a PDI (pre-delivery inspection) on a new CLK convertible in Black. Not sure if it's a 320 or 430, you can guess what I'm hoping for!.........Gilly Gravy Hound

Hey Gilly, if it's a 430 you gotta let me know how she is.

I replaced the relay module and that did the trick! Turn signals and hazards work fine... so that means we're two for two - not bad!

I also replaced the front flex disk. It had deteriorated probably due to a long term oil leak. Gonna' bring her out tomorrow. It's supposed to be awesome weather in NE with temerature in the 90's. It should be sweet!

I look forward to starting on the head. I have a 9,000lb hydraulic vehicle lift with a jib crane in my shop. Just finished installing it this winter. Should work well for the head. The engine has 95k on it. Do you think I should do guides and seals?

Thanks again,

Seals yes, guides no. I have no experience doing the seals with the head off, though, only head installed. Shouldn't be too bad, plus no worrying about "gulping" a valve. Guides will last a heck of a lot longer than 95K, but you can see if they seem exceptionally loose when you do the seals. Getting into nice weather, you sure you want to take it down now? Whatever happened with the hardtop/soft top problem, that fix itself?
Gilly

I do need to take it down. The oil leak got significantly worse after winter storage. The top started working on its own prior to the instrument cluster repar. What' interesting with the top is that the passangers side window does not go down automatically at the beginning of the sequence, but the top drops with now problem. At the end of the sequence both windows power back up fine. I thought that the top would not go down unles the window tripped the down microswitch. I will pull the door panel soon and check it out. The only other thing I have to fix is the power antenna. I will do some basic checking on that.

Turn Signals
 

My problem is that the turn signals and hazard lights go on but don't blink.
Is the solution similar to this one?