Sorry Pierce about starting a new thread. Thanks for moving it back here. I just thought I should since this is a new problem and the other was getting so long.

Again, very helpful info and excellent hypothosis. Strange thing is that I have five pins filled on my headlight switch plug but only four spades on the back of the switch itself. Those spade #s and colors agree with your listing, #4 is the melted wire. The missing spade would engage the pin holding two wires,both yellow & white. The numbers on the plug (very hard to find) do not match up to the corresponding numbers on the switch itself. I think I will dislodge the melted wire (single yellow/white) from the plug and see what doesn't work. Then I'll do the same with the double yellow & white.

My guess is that the rear fog lights are the issue as it's easy to leave those on and I had to replace a rear lens assembly last year which showed signs of excessive heat at the bottom where those fog lights share a double filament bulb with the parking lights. This also exonerates my wife whom I accused of riding the brake whenever I would follow her in a different car.

There's also a white plug taped to the harness behind the HL switch panel It has two of the four slots filled; #1 has two wires, Green & Grey (or lavender) the other Green & Orange. Slot #2 has a single Green & Grey (or lavender). Any idea what this is for? TD

 

green-grey is used for the antenna control wire, does your car have an antenna switch next to the foglamp switch? (mine does, but not sure if all later ones do)

 

Removing the melted wire took out the headlights. The double yellow in the plug that has no mating spade on the switch, shows voltage when the headlights are on, even when it's disconnected from plug and it loses power when high beams are on, thus those wires are only for the fog lights. Scratch my previous thought about the rear fog lights since I now see they are the top light in the lens and the fog light circuit seems to all work fine. Guess that means I should look toward the radio circuit which you mentioned as another source of excess current draw through that melted wire. Since I just put that 850 radio in, that could be the root of the problem. Isn't that what is meant by "shooting oneself in the foot?"

I've never seen the radio light to change in connection with headlight use and I don't care about that and would like to eliminate that wiring, thus eliminate that as a possible problem. You said that the yellow/white goes from HL switch pin #4 to headlight-relay pin #86 and radio pin #6.
-Do you mean #6 on the radio harness plug?
-Does it come from the relay or directly from the HL switch?
-Would it be a yellow/white wire at pin #86 and in the radio harness?

This part will be tricky as I had to cut the old radio harness plug off to connect the plug for the 850 radio, so wire color may be my only hope unless the pin #s are the same for both plugs. If I could just eliminate that wire to the radio at the headlight relay, that would be perfect.

Final detail is how to replace the melted wire? Does it run unbroken to relay #86? I don't feel comfortable just taping up what I can reach through the gauge cluster hole. TD

 

yeah, #6 on the original radio harness plug. if you whacked that off, I dunno what its connected to now, it might just be hanging out in space, and ran into something that caused it to short and melt down. as far as I see,its the only yellow-white circuit at the radio[*]. btw, you CAN buy harness adapters that plug in where the factory radio (and amplifier) connected, so you don't have to cut wires, just splice those harness adapters onto your radio harness.

the wiring diagrams don't show the routes the wires take. they just show that white-yellow circuit can be powered either by the headlight switch in parking lights OR by the headlight relay when the headlights are on, and that it goes to A) the radio, B) the parking lights, and C) the rear fog lamps. the melted insulation suggests that particular branch of the circuit carried too much current at some point in time, and overheated. the other end of the same wire should show overheating too.

re: spades, my guess is, that 'extra' Y-W wire is connected inside the plug shell to the pin of the other Y-W's... (yellow-whites).


[*] the speaker '+' wires are Y-W too, but thats only out at the speaker, at the amplifier, they are other colors

 

wait, if the melted wire took out teh headlights, then it pretty much has to be the wire that powers the headlight relay coil.

now, the wiring diagram shows the wire from the headlight switch going to the radio, then another Y-W from the radio to the headlight relay coil. seems insane to me to wire it that way, but what do I know. I do know the wiring diagrams don't always show the paths correctly.

is it possible at some point you plugged the wrong relay into the headlight relay position K ? there's many different sorts of relays, and even if they have the same shape and pins, they aren't always wired the same, and the wrong relay could easily cause a short.

 

We are getting close. I've got open access to the relays and fuse panel as my new radio & bracket just unbolts leaving everything under the HVAC controls wide open. The yellow/white wire there shows signs of overheating. It was not reconnected to the new harness but was connected to another yellow/white wire that was obviously also in the old harness wiring. When they are disconnected the lights go out. The melted wire has continuity with HL switch#4 and the other yellow/white wire has continuity with pin #86 of the HL relay. When I run a bypass wire in place of the melted wire, all works normally. Still don't have a reason for the wire overheating though.

One more shade-tree mod is that I removed the irritating door chime & seat-belt warning relay a while back. I can't imagine that could be causing a problem? TD

PS There's no connectivity between pin #4 and double yellow/white within the HL plug. It seems like just a place to park that spade without it shorting out on anything. Pretty funky.

 

and that splice of these two Y-W wire segments was well insulated?

 

Yes the spice was very well insulated. The new wire is a little heavier and perhaps I'll solder it and I'll check it periodically . Guess that's all I can do and I'm just happy everything works ... for now!

I'll keep you posted if anything crazy develops. Thanks for all the expert help.

 

I found the best way to improve the headlights on a 940 turbo is to add extra driving lights connected through the dimmer switch, and to have a separate switch to turn them off when not on the open highway.
On my 940 turbo a previous owner had used 80/100 watt bulbs, but the area around the plug ins on the headlights had signs of high heat and melting, so without proper rewiring I would not recommend that.
The headlights on my 97 960 are fabulous, but fitting them into a 940 may not be easy, and they may look odd too!