1989 560SL (w107) gauges went bonkers

[Cole]

Hi,

I'm a '68 pagoda owner with a 560SL problem.
I'm hoping that some of you can help with the apparent electrical/gauge situation I have with this '89 560SL that I just got from the East Coast a couple weeks ago. (I'm in LA.) Basically, a few of the gauges are very erratic and two or three of them start moving at the same time even with the ignition off. For example, with the motor off, if I move the turning signal up or down, the temp gauge and, I believe, the fuel gauge move around.
Other info:
* there's a constant whining noise from the dash that won't stop (so I disconnect the battery);
* there's corrosion on the positive battery head;
* the motor starts and runs well except when I test drove the car, the temp gauge went out the roof even though the car had been driven for just few minutes.
* The car was transported out here from South Carolina and was inspected by an MB dealership there prior to purchase who mentioned nothing about this; during transport, there were one more good rain storms according to the truck driver. There was water in the spare tire well which I removed; there was definite moisture in the right side of the trunk over between the battery and the inner quarter panel; as mentioned, the + head of the battery has corrosion on it (on the main cable attachment and the smaller cable going to it).
* the car has been in my driveway covered for almost three weeks here in So Cal in the dryer weather, but the same problems occurred today when I tested it.

Hopefully, these are enough symptoms to start with.

Thanks very much.
Cole

[cabrioletturbo]

It would help if you locate where the noise is coming from. This remotely is anyone's best guess.
As W107s are notorious for rust underneath the heater box (see pic), if I were you I would inspect that area first, clean up and ensure drain hoses are operational (not leaking into passenger compartment).
Why is this important? As I suspect you may be losing ground somewhere, IF there was rust in the area behind the dash, it could have come (from the heater area) and compromised any of the ground connectors. As you are in SC, may be worth leaving the car open when it is warm and dry, then test for leakages at the front. You may get surprised.

The speedo instrument on 560SL is digital, so pulling it out and checking all the connectors would do good. I seriously doubt you have speedo issue, but that is just me.
Clean the battery terminals, run around with the voltmeter make sure there is no draw-down and if you find an issue, report back.


(not an expert, just common-sense troubleshooting)

[Cole]

Thanks for your reply and good info.
Do you think that a corroded positive battery head could be the source of these erratic gauge problems? Wouldn't it be causing other electrical problems in the car, too?
I tend to agree with you that it's a short or related problem in the dash area.

I appreciate your help.

[cabrioletturbo]

I don't think your issue is positive battery head, but you should clean them both and then work from there on.

[Cole]

Also, the red SRS ("Supplemental Restraint System"?) light is on which was noted before purchase. I don't know what the SRS light is or indicates exactly though have gotten some info indicating that it has to do with the airbags.
So... a couple more questions: does this light relate only to the airbags? If not, what else? Is it related to my erratic gauge problem?

Thanks!

[cabrioletturbo]

Would not know that. You may want to do simple el. troubleshooting, first.

[Cole]

Ok. I just found a good article online about the SRS:
http://www.mercedesmedic.com/srs_airbags/

Next step will be to get the car to a good w107 mechanic.

I much appreciate your help!
Cheerio.
Cole

[450sl]

I have had these symtoms in my 87-500sl ; found a loose connector behind the speedo assembly.  ; takes little time to check.

regards
Mark

[Cole]

I appreciate it, Mark.
I think you were referring to the erratic gauge issues that I mentioned, not the SRS light being on, right?
Also, something that I knew about before buying the car was that the odometer had stopped working about 10,000 miles prior. Neither the prior owner or the MB dealership that did the pre-purchase inspection mentioned anything about the odd gauge behavior, but perhaps there's a connection to the odometer issue somehow. Based on what you and Igor said, the source of the problems appears to be an electrical short or something inside the gauge area.

Thanks!
Cole

[cabrioletturbo]

Check this out:

http://www.peachparts.com/shopforum/mercedes-benz-sl-discussion-forum/186967-560sl-instrument-cluster-wiring.html

[stickandrudderman]

Run a new earth lead from the back of the cluster to the chassis (include a connector for disassembly purposes).
Likely that will cure your problem (but not SRS, which is airbag fault) you'll need to do your research on how to find the fault/blink codes).

[Cole]

Thanks for help with this!

[Cole]

Does anybody by chance know of a knowledgeable, classic MB mechanic in the Burbank, Glendale or Pasadena, California area that could diagnose and fix this erratic gauge issue without a big problem. I'd think that a guy who is familiar with the w107 gauge wiring should be able to spot the cause(s) fairly easily.

Thanks.

[calhippie]

Does anybody by chance know of a knowledgeable, classic MB mechanic in the Burbank, Glendale or Pasadena, California area that could diagnose and fix this erratic gauge issue without a big problem.

Cole:

Try Nelson (the owner) at Boulevard Auto Repair:

Boulevard Auto Repair, Inc.
14857 Burbank Blvd
Sherman Oaks, CA. 91411
www.blvdautorepair.com
(818)989-6028
blvdautorepair@sbcglobal.net

They handle all flavors Benz, and I noticed numerous 107's there when they pulled my 113 transmission recently.  Even if they can't help you, I'm sure they can recommend someone local who can. 

[Cole]

Thanks. Much appreciated!

[Benz Dr.]

Check your over voltage protection relay fuse. If this fuse blows a lot of things will quit working. You can find the relay behind the kick panel just above the fuse box. Red 10 amp use on the top of the relay.