Parking light/blown fuse issue

[lucifer572]

‘86 Carrera Coupé.
Right side parking lights went out. Checked fuse (#3 from front), found blown. Replaced fuse and popped with smoke coming from panel and under dash. Fuses are correct 5A size. Gray wire with black stripe coming from top of fuse panel leading into wiring harness is cooked.




Traced wire in harness to plug thru firewall. Leads to small harness that goes to light switch for parking/head lights.




This same gray wire with black stripe is also cooked.

I’m not too sure how to proceed from here or what could be the cause of the wire overheating. It’s possible there was a short somewhere in the line that caused it?

As a fix, and/or to test the circuit is it possible to run a single wire from the fuse panel to the switch to see if that’s the short. Not sure where the wires go from the switch to the lights.

[86 911 Targa]

^^^^^
The M/Y 86 only has a unique circuit for the right side parking lights.

The diode is associated with the pass side parking lights only.



^^^^^
The diode is located under the dash.

I don't think that a defective diode would cause your issue.

Have a look to see if the diode holder wiring is shorted.

Also, open up the light housings and look for some corrosion,
and, use your multi meter to check for continuity to ground
on the burned wire.

pm me as needed.

Best,

Gerry

[86 911 Targa]

^^^^^
To the R terminal of light switch.


FYI.

G.

[lucifer572]

Well, apparently I’ve fixed the issue. I did a bumperette delete and currently have no license plate lights. I never wrapped the bare ends of the plate light wires. Looking at the plate light fuse being still in place made me think of this. I checked both sides of the plate light wires and sure enough the passenger side contacts were cooked together. This apparently caused the right side parking light fuse to pop and the left hand wire to fry. Repaired the wires in place with liquid electrical tape and heat shrink tubes. Checked continuity btw fuse panel and switch harness. Removed the plate light fuse and replaced the parking light fuses. All lights work, including brake, reverse, and turn signals.

Does this scenario/cause sound correct?

[lucifer572]

One follow up question I have is why the headlights are wired this way, with out #5 right low beam and #8 left high beam being fuses at the top in my pic above?

[Arne2]

Originally Posted by lucifer572

One follow up question I have is why the headlights are wired this way, with out #5 right low beam and #8 left high beam being fuses at the top in my pic above?

Looks like you have a relay kit added for your headlights. That normally would eliminate one fuse each for high and low.

[86 911 Targa]

Originally Posted by lucifer572

Well, apparently I’ve fixed the issue. I did a bumperette delete and currently have no license plate lights. I never wrapped the bare ends of the plate light wires. Looking at the plate light fuse being still in place made me think of this. I checked both sides of the plate light wires and sure enough the passenger side contacts were cooked together. This apparently caused the right side parking light fuse to pop and the left hand wire to fry. Repaired the wires in place with liquid electrical tape and heat shrink tubes. Checked continuity btw fuse panel and switch harness. Removed the plate light fuse and replaced the parking light fuses. All lights work, including brake, reverse, and turn signals.

Does this scenario/cause sound correct?

FYI

The reason for the diode is to turn off the license plate
lights when the "standing lights" are on.

G.

[timmy2]

Originally Posted by lucifer572

One follow up question I have is why the headlights are wired this way, with out #5 right low beam and #8 left high beam being fuses at the top in my pic above?

5&6 as well as 7&8 are common via a brass jumper built into the fuse panel in the back on the top terminals.

[lucifer572]

Thanks, all! If it catches fire I’ll post pics.

[abbygpt]

Does anyone know where I can get a replacement diode? I have checked everything else and I can't get my right marker lights to work when my headlamps are on. 1986 carrera

[kbruz]

Need some help with an 86 Targa. Both my passenger side front light, and rear tail lights are out. I recall that the diode 91161710800 can effect the front light, but was not aware that it also could effect the rear light.

Is this correct?

[Jjason3131]

I have the same issue. Help??!

[kbruz]

Jjason3131.

The diode on the 86 is located right above the ignition key. If the diode is not functioning the right front and rear lights will be out. I had a hard time finding the part. I even wrote the manufacturer in Austria asking if they had they part or could at least send me technical specifications. No luck. I called a lot of shops and finally found one which had the part 91161710800 in stock. I called porsche and they didn't even show the part. I think there is a later revision but I can't tell if it will work

[Steve Marshall]

FYI- For anyone with a 1986 Carrera wanting to get the license plate lights working, read on. It will save you days of brain damage. Before you do anything, locate and replace the fuse pictured below. I could go into extreme detail but I won't because you probably don't care and just want your damn taillights to work. As far as I know, only 1986 Carreras need apply. This fuse might be tucked behind fuse panel. Reach up in there and pull it out. It's not connected to the # 7 license plate light fuse but don't let that deter you. The vague reference to the fuse form the manual is also pictured.