Electrical help needed

[maxhofer]

I'd be grateful if someone can help me in identifying the following problem I'm having on my 1985/1 944 N.A:

Every time I turn on the parking/position lights a cable that goes from the lights switch to the turn light switch (on the steering column) heats up and ends up fried.

The first time it happened I thought the cable was frayed and was making ground. I replaced the cable with a new piece but it happened again, so it wasn't the cable itself. The cable is grey/red by the way.

Anybody know what the problem might be?

Max H.

[rmcdonnell]

You have a short circuit. When you switch on the parking lights, new paths providing 12V through the lights to ground are activated, and somewhere in this chunk of parking light circuit, it is shorted (probably to ground) via an alternative path. This new path includes the grey/red cable that is frying, but the short doesn't have to be nearby at all, though it can be.

It might take some circuit sleuthing, I'll try to dig up the circuits to see if anything comes to mind.
Look for worn or frayed insulation on the parking light looms, maybe near the pop up headlamp mech...

cheers
Rissole

[Vicious]

which wire are you referring to? the one from the steering column switch or the one from the switch left of the column or both. if you have a test light or dmm perform a continuity test one the wires, or if you dont have any of those simply unplug one light at a time till you isolate the circuit causing your short. is your fuse blowing when the wire fries?

[djnolan]

on a late 85.5 there are separate fuses for each light. if the 83 is the same try hooking up a ohm meter to the wire on the column and to ground. Then try pulling each fuse to see where the resistance is lowest. then inspect that wire for shorts.

Also think about where any repairs or accidents might have occurred that could have pinched a wire and caused a short.

It might not be a wiring problem. It could be something is in the light socket causing a short like a piece of a broken bulb base. check all of the bulb sockets first.

If not this, the light wiring in the rear is easy to inspect, just pull out the carpet on the back of the hatch area as if you were accessing the bulbs to change one. On the front it is a little more difficult to inspect as it runs around the spoiler and inner fenders.

[maxhofer]

Originally Posted by rmcdonnell

You have a short circuit. When you switch on the parking lights, new paths providing 12V through the lights to ground are activated, and somewhere in this chunk of parking light circuit, it is shorted (probably to ground) via an alternative path. This new path includes the grey/red cable that is frying, but the short doesn't have to be nearby at all, though it can be.

It might take some circuit sleuthing, I'll try to dig up the circuits to see if anything comes to mind.
Look for worn or frayed insulation on the parking light looms, maybe near the pop up headlamp mech...

cheers
Rissole

Thanks Rissole, I'll check in the places you mention.

[maxhofer]

Originally Posted by Vicious

which wire are you referring to? the one from the steering column switch or the one from the switch left of the column or both. if you have a test light or dmm perform a continuity test one the wires, or if you dont have any of those simply unplug one light at a time till you isolate the circuit causing your short. is your fuse blowing when the wire fries?

Vicious, there is one wire that goes from the Light Switch (left of the column) to the Turn Light Switch (on the column itself). That is the wire my car is burning every time I turn in the parking lights.

[maxhofer]

Originally Posted by djnolan

on a late 85.5 there are separate fuses for each light. if the 83 is the same try hooking up a ohm meter to the wire on the column and to ground. Then try pulling each fuse to see where the resistance is lowest. then inspect that wire for shorts.

Also think about where any repairs or accidents might have occurred that could have pinched a wire and caused a short.

It might not be a wiring problem. It could be something is in the light socket causing a short like a piece of a broken bulb base. check all of the bulb sockets first.

If not this, the light wiring in the rear is easy to inspect, just pull out the carpet on the back of the hatch area as if you were accessing the bulbs to change one. On the front it is a little more difficult to inspect as it runs around the spoiler and inner fenders.

Djnolan, I'll check on those, thanks!!! will post results.

[djnolan]

Max,

Also make sure you have the correct fuses installed. Check them all. It is difficult to understand why a wire would melt without blowing the fuses or melting the switch contacts first. If the fuses are correct then maybe the short is between the fuse panel and the melted wire.

The problem sounds very peculiar. I have a late 85.5 car and don't know the early car's electrical system so I may be sending you on a wild goose chase. You should have a look at a wiring diagram if you have tried all of the above and haven't found the problem by now. Maybe there is some incorrect wiring if all of the above hasn't worked

[rmcdonnell]

Hi Maxhofer,

I've tried to find some diagrams, I saw the electrical ones for a 1984 944 on Pelican, sheets 2,1 and 2,2. There are a number of grey/red wires that go to the RH parking lights. These are switched high with the parking light switch, to 12V. (Point 58R on the light switch)

Try pulling fuse 13, (sheet 2,2) and see if either side of the fuse socket is shorted to ground.

Take out the bulb on the right side, and see if the fuse socket is still shorted on both sides. (It shouldn't be on either, but it points to possible causes if it is).

Find point 58R on your light switch. Check if this is shorted to ground. (It shouldn't be, but would explain why the wires get very hot).

Anyway, I think you have a short to ground on this side of your parking light circuit. You may be able to track it down with a continuity buzzer, using some of the techniques above. It may well be a chafed wire touching ground, shorted bulb, duff wiring at fuse 13 etc.

Best of luck.
Cheers
Rissole

[maxhofer]

Thanks again Rissole, I will do the tests tonight.