Looked for threads on smoke from dash and found nada, so here I go...
Son's 72 had after market wheel and hub that were not connected to the horn. I lent him a standard 914 wheel/hub with batwing. Everything went together just fine, and horn worked fine. While sitting in the drivers seat I noticed that the bezel on the headlight switch was loose so I pulled on the switch while rotating it to the right to tighten it. Smoke started pouring out from under the dash so I quickly shut it off. Lots of smoke. He later drove the car and it started blowing fuses. Now no headlights, turns or brakes.
What happened?

Check the switch & the fuse panel. Something shorted to ground. Chances are burning wire insulation produced the smoke.

Plus, the burnt wire can take out a number of wires in the loom next to it and the smoke can pour out. Had it in a 79 911Sc targa

Bob B

By rotating the switch, one of the hot wires on the side of the switch made contact with ground. Either another switch/wire or parts of the metal dash sub-frame.

I would pull the steering wheel, the lower knee pad gauge cluster and top dash cover cover to get full access to the metal sub-frame and inspect every single switch and wire in the loom.

And don't forget to disconnect the battery before you start digging into this ...

I was not clear in my description. The knob on the light switch was loose, so I screwed it on. I didn't rotate the switch in the dash or the bezel...my bad. Just the knob to tighten it. I wonder what the coincidence of installing the steering wheel and connecting the horn? I will see if the horn still works. If it does, and the fuse is good, I guess that rules it out as the culprit.

I agree with @SirAndy .

In your initial description, you mentioned that you held the light switch (in the "on" position) while tightening the light switch bezel.

I'm guessing the switch itself rotated (due to the dimmer switch motion) while the bezel was being tightened.

The rotating switch then caused a "live wire" contact with something it shouldn't have.

Where exactly did the smoke originate from? (ie, did the smoke come from the area of the light switch or from the area of the steering column?).

Regardless, you'll have to start some disassembly to determine what part of your harness became fried...it should be obvious.

I will re-iterate again...disconnect the battery before starting disassembly.

Good luck.

Please don't. I would not turn on the key until you have replaced all melted wires. In fact, i wouldn't even let the car sit overnight with the battery still connected.

Plenty of wires in there that are hot without the key and if one of those is even slightly compromised, you could wake up to a burnt down garage.

Battery disconnected...will advise.

Here are a couple of links that show how things are supposed to look. As long as all of the insulated spade lugs were installed it doesn't look like there could be an easy way for one of the contacts to short to a nearby ground.

The other link covers the internals. Maybe your switch just burned out internally? That would be the best scenario even if replacements are expensive or hard to find.

https://www.google.com/search?q=porsche+914...=AVT_UHmq2LteFM

https://www.pelicanparts.com/techarticles/9...lamp_switch.htm

Ron

Ok, it starts to get exciting. Took the bottom of the dash and the three gauges out for access. Removed the three left switches...light, fog and hazard. Initially all the wires looked ok connected to the switches. Further examination showed the white-green wire from the light switch to the bottom of the speedo was fried in several places. That wire is connected to the front center of the light switch. When removed from the back of the speedo, there was no attached bulb. We guess that the bulb was not securely trapped in the holder...got cock-eyed and shorted. That wire's amperage is affected by the rheostat in the light switch that adjusts the "back lighting" for the instruments. When I noticed the knob on the switch was loose, as I tightened it, I also turned the rheostat which increased the amperage to the short which fried the wire. Replaced the wire and now the lights and side markers all work...but still have a right side turn signal issue as well as a hazard issue. Pulling on the hazard switch blows fuse 11 and right turn switch blows fuse 9.

These issues could all be related, or not. With the steering wheel off, we have access to the turn switch assembly...and without removing it, nothing looks amiss. As the left side turn signal works, I'm not thinking relay or flasher...maybe a bad bulb would cause a short to blow a fuse? But there is some wiring diagram confusion. My diagram is for a 914-6 and maybe it differs from a 914 diagram? Where the white-green wire connects to the middle front of the light switch, the diagram shows twin white-green wires. One goes to the bottom of the speedo (fried wire) and the other end goes to the #52 flasher. Unfortunately, the white-green wire on my son's car isn't a double, but a single. And we can't figure out where the flasher relay is in the dash.

Could a faulty flasher relay cause one turn signal to blow a fuse. We can't see any other problem wires. And the hazard switch blows a fuse too...hmmm.

As always thanks for the help and suggestions.

Very much so. Your '72 /4 should be close to a '71 /4.

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That is how I got an oil leak coming from the radio in my TR6. Shorted wire burned through the plastic hose to the oil pressure gauge, didn’t catch fire, but started dripping oil onto the old AM radio.

So hazard switch #31 and direction blinker #47, share a common ground at ‘ground connection point B’ #83 on diagram.
Any problems with your door buzzer switches or interior light?

.

Wow, that sounds like classic British sports car engineering: combining leaking electricity and leaking oil.