PeachParts Mercedes-Benz Forum - View Single Post

Jeremy5848 · #5 06-13-2010, 05:22 PM

I've noticed that if you look closely and thoroughly (as you have obviously done), the manuals don't always match what's in the car. It also depends on which manual you have. I see that on my own '87 from time to time. You have to live with it, unfortunately.

Your ground point W9 is in my factory Electrical Troubleshooting Manual (ETM) located at the "lower left front of engine compartment." There is also a ground point W2 which is located at the "lower right front of engine compartment." Make sure you're not confusing them.

W9 grounds the left headlamp and W2 grounds the right headlamp. The "Ground Distribution" page of ETM shows a total of five (5) items grounded at W9:
1) K2 Headlamp Washer Relay
2) M6/2 Left headlamp washer motor
3) S32 Refrigerant high pressure switch
4) M4 Aux fan
5) E1 Left headlamp
My car has only three (3) wires at this point, perhaps in part because I have removed the headlight wiper assemblies when I installed Euro headlamps.

W2 has seven items grounded including the right headlamp and its washer motor, the horns, both washer pumps, and more. I cannot see W2 because the air cleaner is in the way.

My ETM shows that Fuse 3 supplies lamps (park/side marker/license plate), the instrument cluster and center console illumination, and both headlamp wiper-washers.

One problem I had some time ago involved an electronic relay, N40, the Instrument Illumination Control Unit. Located behind the instrument cluster, N40 is in effect an "amplifier," allowing the rheostat (dimmer) in the cluster to handle many more lamps than it would otherwise be able to do. If it shorts internally, it will blow fuse 3; you can remove every lamp in the car and N40, if bad, will still blow fuse 3.

Here's a test that might work and will be easier than removing the cluster: turn the dimmer rheostat all the way down to "off" and replace fuse 3. Now turn up the dimmer rheostat and see if fuse 3 blows. If it does, the problem is somewhere in the instrument/cluster/console area and I would check N40 first. Remove the instrument cluster and then remove the plug from N40 (easier than removing N40 itself, the plug is where you can get at it). Does the fuse-blowing stop? If so, N40 is bad.

Jeremy