Wayne: I got a bunch of stuff printed out at work today. I didn't really spot any service information bulletin relating to the problem. Yes, I'd like to attack the cluster problem first, it may lead to the other problems. First I'll read off the first 3 steps in diagnosing a "dead" cluster, realizing the cluster isn't totally dead, they didn't have a test for this exact problem. You are going to remove the cluster and test sockets at connector 1 and 2, these are the large connectors with the sockets arranged in a circle. Connector 1 is the one on the left (when the cluster is installed, the one on the drivers door side) and 2 is the right side. Test step 1.0 is voltage supply circuit 30 (hot at all times, so key can be left off for this step). Connect a voltmeter to socket 11 and 12 on connector 2, should be battery voltage. Test step 1.1 is voltage supply circuit 15 (hot in run or start, key is turned to "ON") Connect your voltmeter to socket 1 and 10 on connector 1. With key "ON" should be battery voltage. Test step 1.2, also circuit 15, connect your voltmeter to socket 5 and 10 on connector 1, also should be battery voltage with ignition "ON". I assume you have enough electrical knowledge to comprehend all of this. I hope so, because I am going to explain the tests you just did. On test step 1.0, socket 12 on connector 2 comes from fuse 9, an 8 amp in the main fuse box. Socket 11 is ground provided by W11, I believe this is located on the engine. On test step 1.1, that socket #1 on connector 1 is unfused circuit 15, from the ignition switch via the powered side of fuse 5, not the fused side. If it fails that particular test, I would assume either a bad ignition switch terminal, or a loose screw on the fuse box bus. I would also assume it is going to fail test step 1.2, I'll explain later. On test step 1.1 now, the other socket(connector 1, socket 10) is ground, provided at W1, which is located behind the cluster off to the left, you'll see a mass of brown wires, there are actually 2 10mm bolts connecting these wires to ground, that's all considered W1. OK, onto test step 1.2, That is also circuit 15, but it is fused, comes from the fused side of fuse 5, that's why I say if it failed test step 1.1, it sure as hell is going to fail this test step also. I t COULD pass test step 1.1 and fail this test step if fuse 5 is blown. It uses the same ground as test step 1.1, the one behind the cluster. Now then, if this all checks out OK, per the electrical test program I have, the problem SHOULD be the electronic circuit board. I did some checking today on that, it is still available seperately, it cost more than I remembered. I also got some parts info on it. On a 129 without ASR, the P/N is 129-540-48-47-91. I believe the price on it was about $430. WITH ASR, the P/N is 129-540-71-48, and add a "80" behind that part number for a reman. I couldn't get a price on that one, as our computer in the parts dept is now busticated. The parts guy said something like "the number for that one is 'blocked'" I asked him what the hell that means, he said it means they will need the VIN number to order it........Don't ask me I only work here. Hopefully the electrical test program will help sort out what is all going on with the car and it won't come down to fixing the cluster then figuring out what else is broke. My money is on the ignition switch being bad, but we'll see. There are several terminals coming off and it wouldn't be the first one I've seen cause problems in one area of the car and leave other systems unaffected...Gilly

WOW! What a lot of info... I really can't thank you enough for taking the time to help. This forum is such a valuable resource. I just hope I can repay through helping others as you do.

I'm good with electronics so I will step through your test program after work tomorrow night. Interesting that you feel the ignition switch might be the root cause.

I will report my results.

Thanks again,

__________________
-Wayne

1994 E320 Coupe (120k)
1990 300SL (BBS,RENNtech adds)
1988 260E Sedan (180k)

Wayne, no prob. Don't forget if it fails that second step (1.1) to think about pulling up the fuse box guts and checking the tightness of the screws of fuse 5. At least I think that's the way to go, I can't remember now if that has the ceramic bullet fuses or the plastic twin-blade ones. the bullet fuses would have screws under the fusebox holder, I've seen these loosen up with time and heat and cause various mysteries. I'm thinking it will pass 1st step (1.0) based on the fact that the clock keeps working OK. If it fails test step 2, I wouldn't hardly worry about test step 3. Go ahead and check it, I guess. Weirder things have happened, look at me!!!.....Gilly

Gilly, I had the guts of the fuse block up and checked around for anything unusual. I didn't think to check the terminal screws. The car does have the ceramic fuses. I'm tempted to bail on work tomorrow to stay home and check it out

__________________
-Wayne

1994 E320 Coupe (120k)
1990 300SL (BBS,RENNtech adds)
1988 260E Sedan (180k)

Oh, sure bail out on work will ya? Gee, if you worked in a Mercedes shop, every day would be like "bailing on work"!!!! Anyways, as the boss always says "do the test"! Gilly

Wayne,

You have got a great looking SL. I like that front bumper and love the Xenon lights (I am considering the lights as well). I like the model 97 front fender panels and model 99 taillights and side mirrors!
I have been thinking whether to upgrade my silver-gray 1990 300SL or whether to buy a newer SL first, but after seeing these pics, I think I will stay with the current one!

I don't know how far you are by now and what problems are solved, but about the flashing top-switch: I had a flashing switch as well because my hydraulic system was not able to close the hard or soft top anymore. It took a new hydraulic valve to get it working again.

The indicators/hazard lights sound like a hazard switch or combi-relays problem...

greetingz,

__________________
1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)

Well Gilly, it looks like the results from the 3 tests you gave me point to the cluster being bad after all. This probably means I will have to chase down each of the other issues individually.

If it wasn't for the kind comments like the one above from MBenz I might lose faith... nah! (just a weak moment). Thanks MBenz - it seems we have similar MBs.

Back to business:
All 3 tests came back positive. The car does not have ASR so it looks like the part# I need is 129-540-48-47-91. What's your feeling on the reman units?

I included all of the terminal to terminal test results below for reference, including ones having the engine running.

Let me know if you agree with the next step being to purchase a new cluster circuit board (either reman or new).

Connector #1
==========
Terms---IgnOff--IgnOn---EngRun
------------------------------
10-01----0v-----12v----12v
10-02----0v------0v------0v
10-03----0v------0v------0v
10-04----0v------6v------6v
10-05----0v-----12v----12v
10-06----0v------0v------0v
10-07-no terminal
10-08----0v------0v------0v
10-09----0v------5v------5v
10-10-same terminal
10-11----0v------0v------0v
10-12----0v------0v------0v
10-13----0v------0v------6v
10-14----0v------0v------0v
10-15----0v------0v----12v

Connector #2
==========
Terms---IgnOff--IgnOn---EngRun
------------------------------
11-01-no terminal
11-02----0v------0v------0v
11-03----0v------0v------0v
11-04----0v------0v------0v
11-05----0v------0v------0v
11-06----0v------0v------0v
11-07----0v-----12v----12v
11-08----0v-----12v----12v (drops to 10v w/^rpm)
11-09----0v------0v------0v
11-10----0v------0v------0v
11-11-same terminal
11-12---12v-----12v----12v
11-13----0v------0v------0v
11-14----0v------0v------0v
11-15-no terminal

Thanks,

__________________
-Wayne

1994 E320 Coupe (120k)
1990 300SL (BBS,RENNtech adds)
1988 260E Sedan (180k)

Yeah, I'm thinking reman, the warranty is the same, 1 year, unlimited miles. First off I should point out just a couple quick things. The test "we" did is for the cluster being inop, it of course was the first basic step you would do if the cluster were totally dead. You're not totally dead, but hey, there's no test step for "cluster dead except clock and coolant temp are ok, so's the illumination and it seems like the warning lights work", so this is the best I could do, it's what I would do in the shop. Also I'll point out that at the end of test step 1.2 (the last one), it states "value OK=electronic circuit board. Now, I was looking the wiring schematic over some more after getting your last post. Her's one thing I am curious about: What effect does it have on the cluster if you pull fuse 9 or fuse 5? Pull one of these out and check out the operation of the cluster, then put it in, pull out the other and also see what effect it has on the cluster, in other words does it kill the clock, temp gauge, warning lights? Just a little self-test I thought of. The whole thing gets more confusing the more I look at the diagram, though. it seems like if you had problems with pin 12, circuit 30, that the clock wouldn't work. If you lost pin 1 circuit 15, most of the warning lights wouldn't work (BTW, does the generator (battery symbol) light come on, key on engine off? If you lost pin 5 circuit 15 the engine temp gauge wouldn't work. Maybe its a ground problem with the electronics board. I mean, these can do some crazy things with a bad electronics board. The wiring diagram makes it look so sensible how everything should work, but the wiring diagram is just that, it can't show you exactly how the circuit is layed out in the cluster or on the circuit board itself, so I think maybe it would be best to stick with the test results you have and hope for the best....Gilly

I checked the impact of pulling fuses #5 and #9 on the response of the gauges and lights when the ignition is on, but without starting the engine:

------------------------with all---with #5----with #9
------------------------fuses in---fuse out---fuse out
Fuel Gage------------------N---------N---------N
Low Fuel Light-------------Y---------Y---------N
Coolant Gage---------------Y---------N---------Y
Low Coolant Light----------Y---------Y---------N
MPG Gauge------------------N---------N---------N
Odometer-------------------N---------N---------N
Speedometer----------------N---------N---------N
Turn Signals---------------N---------N---------N
Turn Signal Indicators-----N---------N---------N
Tachometer-----------------N---------N---------N
Clock----------------------Y---------Y---------N
Oil Pressure Gage----------N---------N---------N
Low Oil Pressure Light-----Y---------Y---------N
High Beam Indicator Light--Y---------Y---------Y
Washer Fluid Level Light---N---------N---------N
Bad Bulb Indicator Light---N---------N---------N
Low Brake Fluid Light------N---------N---------N
Air Temp Indication--------N---------N---------N
Low Battery Voltage Light--Y---------Y---------Y
ABS Light------------------Y---------Y---------Y
SRS Light------------------Y---------Y---------Y
Check Engine Light---------Y---------Y---------Y
Seat Belt Warning Light----Y---------Y---------N

Seems like with so many things not working that the circuit board is a good bet. Either that or I'm trying to talk myself into it!

__________________
-Wayne

1994 E320 Coupe (120k)
1990 300SL (BBS,RENNtech adds)
1988 260E Sedan (180k)

Wayne: One last thing. Press "in" on the clock adjusting knob with the key "on", hold it in for at least 5 seconds. Watch the outside temp display. You may get a weird display, a 2 digit number followed by a decimal and a "|". Does it do this? Email me with the results, we are cluttering up the whole site with this stuff. email gillybenztech@yahoo.com.....Gilly

Well, thanks to gillybenztech the problem with the instrument cluster is solved. I replaced the instrument cluster circuit board which is actually everything but the gauges and the front lense. This took care of the mystery of the gauges not working. Please see prior posts on this topic for the tests Gilly provided which lead to the correct diagnosis. The part cost me ~$412. I still have some other electrical gremlins to work through regarding the turn signals, but I wanted to post how the instrument cluster problem was solved.
Thanks to all,

__________________
-Wayne

1994 E320 Coupe (120k)
1990 300SL (BBS,RENNtech adds)
1988 260E Sedan (180k)

That's great, Wayne. I'm always a little nervous about this stuff (recommending solutions over the net) because I'd feel so bad if it doesn't work out to be correct. Easier at work, if I'm wrong, pull it out and give it back to parts. The boss and parts dept. are pissed off for a little while, but what the hell, they aren't perfect either. Besides that, how long can ya stay pissed at a swell, helpful guy like me? On the turn signals, kinda give me the run-down on what exterior lights are working or not. When you try the signals, are the bulbs just not lit at all, or do they come on but don't blink? Could be a few things, exterior lamp monitor (module) come to mind, but again, better to do some common sense testing than throw (expensive) parts at the problem.....Gilly

Gilly, I could not have done it without your help. Your boss can't stay pissed at you for long... such a helpful guy and all.

The turn signals don't do anything, same for the hazard lights. The bulbs go on when I turn on the parking/head lights, but nothing with the turn signal or hazard light switches. No blink, no relay clicking... just dead. I was thinking either a relay or the hazard switch itself. As you know I've been all through the fuses.

I will be going on vacation for a couple days so I won't be able to get back to working on the car until next weekend. I will look for this thread when I return to see what ideas you might have on this.

Thanks,

__________________
-Wayne

1994 E320 Coupe (120k)
1990 300SL (BBS,RENNtech adds)
1988 260E Sedan (180k)

I’m sorry to bother you guy’s but, this is almost the same problem that I have with my 500SL 91. The soft top, roll bar and the instrument cluster stopped working. The temp gage and the dummy light on the cluster still work, but every thing else ‘nada’! I would really like to know what suggestions do you have on solving this problem. P.S. if you could send me some pictures of your SL.

__________________

2001 C320 Sport 17" AMG Potenza S03
1991 500SL 18" AMG Contysport
1993 190E 2.6 17" AMG Contysport
2002 G500