W126 #9 Fues blows - Door light glows when closed, chasing melted wires :( 1981 300SD - PeachParts Mercedes-Benz Forum

VintageBenz.org · #1 07-02-2009, 02:42 PM

So a few months ago my now wife plugged her cell phone in for a charge in the right rear cigar lighter. Well the PO apparently had the tip to one of his chargers break off in there and the second she plugged it in *POP* #9 fuse blew. So I removed the debris, replaced the fuse and went to start it back up. Turned the key *POP*. ****.

We are taking the ole girl on a nice cruise up North for the weekend and the stereo is on the same circuit. I began testing for continuity between the positive and ground of the cigar lighter plate. Sure enough there is. I carefully removed the door panel (the interior is in such good shape I hate to even have to work on it) and looked for signs of any wires that may have melted together. None that I can see. I tried to follow it up as far as I could to I can remove it from the circuit for the weekend.

Any pointers? We leave around 6 today and the wife doesn't want me to spend too much time chasing this. Music would be very nice on the trip up however

I'll have internet access up there and I am bringing my Chilton and Hanes manuals so I might spend a few minutes trying to get it to work.....

Oh the joys!!

Thanks guys,
Bryan Plaunt

#2 07-02-2009, 03:09 PM

Voltage relay...mine is on the back of the alternator.

toomany MBZ · #3 07-02-2009, 03:20 PM

If you can unplug the power to the lighter and install a new fuse in the panel, you may have music.
As far as the glowing door light, I don't have a clue, but checking the voltage regulator can't hurt. Yet that usually causes a glowing battery light on the dash.

tbomachines · #4 07-02-2009, 03:23 PM

Hm very odd, perhaps the door switch that controls the courtesy light melted with a spike of current, and that is causing both problems? Completely out on a limb with that, not sure if they are even on the same fuse

VintageBenz.org · #5 07-02-2009, 06:07 PM

Thanks for the help guys.Unplugged the wire from the lighter and installed a new fuse, turned the key and *POP*. I'm going to check my references and see if they are on the same fuse, but we are out on the same limb. Problem is it must be pretty far up the wire because I did not see it even with the door panel off.Anyone know where it goes once it gets back into the cabin? Should I start from the fusebox back?Thanks again to all those in our family of proud Mercedes owners.

toomany MBZ · #6 07-02-2009, 07:50 PM

#9 fuse is for the lighter says radio too, (among other things) yet fuse #13 is for the electronic radio, (among other things) go figure.

ashedd · #7 07-02-2009, 08:47 PM

I dealt with this on my 300D... I must assume the two cars have similar designed circuits.

The interior lighting,door switches,radio,lighters all co mingle in or about the same harness. If any of those above circuits get hot enough to melt wires it will take out the surrounding circuits. The number 9 fuse is probably the "bad" circuit but many many wires can be fried.

Basically you have to follow each wire in the harness and inspect it. You also can isolate each circuit at the fuse block and measure the current draw. A quick fix might be to take all the wires off the back of fuse 9. Apply a FUSED 12 volt source to each wire until you find the one that turns the radio on. Leave all the other wires off and reconnect the radio wire. This will only work if the wire running from the fuse to the radio is ok.

1/3 of my harness was melted... I rebuilt the whole thing. Sorry to scare you

VintageBenz.org · #8 07-08-2009, 10:23 PM

Well I lifted up the fuse panel (surprisingly easy) and used a FUSED power wire to test the two leads that were attached. The one with the thicker shielding labeled #9 caused the fuse to blow right away. The other caused the radio to turn on! I can not thank this forum enough. Thank you all very much for your help!

Bryan

polarisrmk · #9 07-09-2009, 12:32 AM

I had the same problem with glowing door light when the door was closed on my 85 126 check the switch above the climate control that has a picture of a light on it.... it has either been bumped on or has malfunctioned.... mine somehow got full of soda from the po i cleaned it out and no more light on with the door closed.

ashedd · #10 07-09-2009, 01:30 AM

I forgot about this thread.

Glad to hear it worked out. If nothing is missing from that bad circuit that you cannot live without(interior lights maybe) then I would leave alone, for now. It really is a PITA to mess with the harness. I had my dash, carpet, A pillar covers, fuse block, relay block, drivers seat, center console ALL removed to fix the wiring. Then I had bugs to work out after it was done. I chase sparks in Helicopters anyway so it was really not that big of a deal for me. But it still wasn't a walk in the park. One method you might try is the one I use to paint walls.. I HATE painting but if I drink beer in the process it doesn't seem quite as bad. Takes longer that way.