1988 300 DS - Electrical Problem - PeachParts Mercedes-Benz Forum

ky gravy · #1 11-03-2009, 12:14 PM

Here is what does not work - anything in the instrament panel except for the glow blug light. Headlights and brakelights do work - turn signals do not.

I believe it is probably a loose ground... I have been unable to locate a wiring diagram to trace back the problem. Also, it occurred to me that it might be one of the fusible links located in the fuse box but not labeled.

Help me, please.

PS. I didn't mean to close the earlier thread....sorry.

Jeremy5848 · #2 11-03-2009, 12:50 PM

I do not know what your car is -- but make sure that you actually remove each fuse from the fuse holder and confirm that it doesn't have any hairline cracks and that the ends are clean and shiny.

toomany MBZ · #3 11-03-2009, 02:07 PM

Agreed, clean or replace all the fuses, see what you've got then.

ky gravy · #4 11-03-2009, 06:50 PM

checked all fuses one was blown but that was for A/C whichhas never worked...but not the large square silver blocks in the fuse panel. Are they fuses as well? Horn works and all of the lights in the lower section...battery, glow plug, etc. come on.

ky gravy · #5 11-03-2009, 06:52 PM

in case it helps, the car is an 83 300 SD not DS.

Jeremy5848 · #6 11-03-2009, 09:13 PM

Ah, an SD. That's helpful. The "large square silver blocks in the fuse panel" are relays. AFAIK, they have nothing to do with the dash lights -- someone please correct me if they do. Additionally, there are several chassis grounds used by the panel lights -- one behind the instrument cluster, one in the console, in addition to the one in the cluster itself. Unlikely that one bad ground would cause you to lose all of your lights.

I would check the rheostat (dimmer control) in the instrument cluster next. All of the dash and console lights are operated through that rheostat. You have to remove the cluster, then you can remove the rheostat and test it, replace it, or put a jumper across it.

The gauges themselves have their own fuse but I don't know which it is for an SD. The gasser section of this forum added a section on fuse cards for all Mercedeses; you might look to see if you can find your car listed.

The gauges could also have a bad ground but as many of the gauges are operated by a sensor that connects to ground, it is unlikely that all are bad. More likely that the hot lead to the gauges is bad or (again) a fuse. In my '87 300D (a 124, different from your 126 car) all of the gauges work off of fuse #5, except for the clock, which is on fuse #9. Your car should be similar but maybe different fuse numbers.

Jeremy

charmalu · #7 11-04-2009, 12:33 PM

I just went through this same sort of problem with my 85 300D.

My temp gauge would work, then suddenly jump up, then peg up against melt down at the top of the gauge.
thought I had some sort of a ground problem between the gauges in the back, but too lazy to get into it............... until

I turned the key one morning and nothing, dead like some one stole the battery.
horn worked, head lights nice and right. turn key, no glow plug or anything else lighted up, but a weak battery light. remove key and Batt. light stayed on

.

Bottom line after a bunch of checking, hair pulling and finally posting a ? here. It was the ground strap between the engine and body of the car. It was tight, clean etc........the bolt that clamps the ground to the engine/transmission had enought paint it wasn`t getting a good ground.

Sanded off some paint for a good ground, and all is well.

The ground strap is on the drivers side under the car. 17mm bolt on engine/trans. and I believe a 15mm bolt on the body.
Your SD should be the same.

Charlie