Headlight switch smoke

[dsscpa00]

1988 Porsche 911 Targa

I installed 9Haus LED headlights and halo DRL/turn signals. All tested fine but after a bit of time there was smoke from the switch area in the dash. Shut everything down and no more smoke. Also of note I have the speedo out for repair so those gauge light sockets are hanging waiting for the gauge to return.

Not sure if there is a ground issue with the gauge lights unrelated to the headlights… or ?

[dsscpa00]

I put the old Porsche oem headlights back in and still smoke… so that rules out the headlights.

Is having the gauge out with light sockets unconnected the issue?

[911obgyn]

Unfused indicator light circuit will cause smoke and all kinds of headaches. There are threads on putting a fuse in there. Something you should do while you are in there.

[JonS]

There is a relay kit so the stalk does not switch the load current of the bulbs. Host has it.

[dsscpa00]

Originally Posted by 911obgyn

Unfused indicator light circuit will cause smoke and all kinds of headaches. There are threads on putting a fuse in there. Something you should do while you are in there.

I added a fuse to to 58a the instrument circuit. Now when I switch the lights on tge 2amp fuse blows instantly. Headlights, signals all working now as they should

How do I begin to figure out why the fuse is blowing when I pull the headlight switch on? Could the switch be shorting internally and blowing the fuse? If not then what next? Pull all of the gauges?

[dsscpa00]

Originally Posted by JonS

There is a relay kit so the stalk does not switch the load current of the bulbs. Host has it.

I ordered the relay kit from pelican but more as a precaution as the headlights and signals are now working,

Need ideas on how to pin down why the fuse I added to 58a off the headlight switch keeps blowing.

[timmy2]

One of the 8 gauge lights or wiring to them is shorting to ground.
Fuse blowing is the result.

[dsscpa00]

Originally Posted by timmy2

One of the 8 gauge lights or wiring to them is shorting to ground.
Fuse blowing is the result.

So having never had to troubleshoot this before, I start by pulling the gauges and tracing each bulb wire looking for damage that would ground?

The speedo is out for repair. I had the clock and fuel gauge out for other reasons…are the metal light sockets grounded to the metal in the gauge? Would having them out off the gauge affect the ground?

[JonS]

58a has 3 circuits on the terminal. 1. to flasher relay via a resistor. 2. to the 4 dash lights in the fresh air blower and 1 in the defroster sign square on the tunnel.3. To fog light switch light, defroster switch light and all of the guage lights.

They are dimmed by rotation. Voltage control for incandescent, no LEDs should be here. I would suggest hunting for loom damage in those areas. Also check wiring at the terminals at the headlight and flasher
switches. Looks like that fuse thread landed on 3A in 2021 "Dash lighting fuse installation". Yes the Speedo and it's lights share a ground in the 84/85 workshop manual.

[911obgyn]

Check where there was smoke, melted wires may be stuck to ground or other wires.

[dsscpa00]

The smoke was at the headlight switch, no obvious wire damage there. Headlights and parking lights all work.

The Lights on the vent panel work as well as the lights connected to the flasher. So by process of elimination that leaves the gauge lights - they’re not working - I keep coming back to the fact that the speedo is out for repair so those light sockets are not connected to the gauge and perhaps they need to be in the gauge housing to complete the ground circuit.

[JonS]

Originally Posted by dsscpa00

The smoke was at the headlight switch, no obvious wire damage there. Headlights and parking lights all work.

The Lights on the vent panel work as well as the lights connected to the flasher. So by process of elimination that leaves the gauge lights - they’re not working - I keep coming back to the fact that the speedo is out for repair so those light sockets are not connected to the gauge and perhaps they need to be in the gauge housing to complete the ground circuit.

58a purple. Ground in Speedo and to body in green. Still unsure of extent or location of burnt wire insulation. My thoughts would be between switch 58a and where it splits to all these bulbs.

[blucille]

Yes. The gauge lights only have a Single wire attached to them. The body of the light socket uses the body of the gauge as a ground. I was under the impression that some of your gauges were still installed. Those gauge lights should work.

[pmax]

Originally Posted by dsscpa00

The smoke was at the headlight switch, no obvious wire damage there. Headlights and parking lights all work.

9Haus or Porsche OEM ?

[dsscpa00]

Originally Posted by pmax

9Haus or Porsche OEM ?

Tried both and both worked fine eliminating them as the cause.

[dsscpa00]

Speedo is back and reinstalled, still blowing the fuse I added and no gauge lights. Can remove all of the bulbs and add them back one by one till the fuse blows? And/or pull the gauges and look for where the wire branches off to the gauges?

[dsscpa00]

Originally Posted by dsscpa00

Speedo is back and reinstalled, still blowing the fuse I added and no gauge lights. Can remove all of the bulbs and add them back one by one till the fuse blows? And/or pull the gauges and look for where the wire branches off to the gauges?

Four wires behind speedo not connected to anything…?

[dsscpa00]

Originally Posted by JonS

58a purple. Ground in Speedo and to body in green. Still unsure of extent or location of burnt wire insulation. My thoughts would be between switch 58a and where it splits to all these bulbs.

So a workaround would be to re-wire the lights single wire straight to 58a and bypass whatever ground issue is in the bundle ?

[famoroso]

It won't address any ground issues, but if you're interested in a replacement gauge illumination harness, I have a new one available. It is constructed with 16 AWG wire instead of the smaller gauge wire Porsche used and it's branched, instead of having all wires run to one point.

[JonS]

4 wire ends? Something else in the car is not functioning. Trace the 4 wires to what terminal they land on the other side. This might illuminate a past issue in the loom.

I don't disagree with replacing the light loom. There is more investigation needed. 146 branches into a wire to the bulb in the fog light switch that is dimmed and a light in the heater console between the seats. Those would be out with the fuse blown.

Suggest some battery disconnected continuity checks of this wiring end to end and to ground. If the wiring is going into looms.you should find those circuits and see if you have continuity line to line. The 58a is traveling to the console between the seats to a 6 pin connector. This may be worth investigating.

Do the football blowers on both sides function properly? Looks like 58a is also powering a relay that switches those from the heater control panel. That relay is a place where another 25 amp protected circuit is in proximity.

There are a few unprotected circuits in these cars. It is worthwhile to do the relays and this lighting fuse