DaveN

Great way to start the day
I have a new to me 91 S4 that I have been driving for 45 days. Working out the little niggles from low miles and garage storage.
I have used my running lights and head lights with no issues at all.
I ordered a full set of LED festoons and headlight/fog bulbs from Woodypeck.
Installed the festoons and popped a fuse; ha, dumbass here knows it's better to pull the fuse. Replaced, all good.
Put in the headlights and seemed great. Only tested for a few seconds.
Changes the fog/driving bulbs and tested again. Had the switch set to running lights and full headlights.
Waited a bit longer this time and noticed white smoke coming from the headlight switch
I figured maybe too much un-relayed draw from the headlights. I disconnected all 6 lights in front and now
I still have smoke (very little smell at all, just a mild a "warm" electrical smell) everytime I turn on the running lights.
I wish it was easy to pull the switch and find the warm wire but that looks like a pod removal
Any wizard suggestions out there?

StratfordShark

No need to remove pod. Pull off the top of the switch, revealing the bulb and two spring tabs. Squeeze tabs in and pull the whole assembly out of the pod. Not much in way of slack but may be enough for you to see which wire is carrying excess current.

DaveN

Brilliant! I was wondering about the 2 indents I saw but most vids I have watched were all about pod and cluster removal so I assumed the worst. 😁
I have a hunch the new LED bulbs drew too much current. I have the shop manuals so I can see if the headlights are un-relayed and passing through the switch.
Hopefully I don't have a mystery wire shorted in a loom, that would be bad. I'm loving the car.

Zirconocene

I'd be surprised if you found the LEDs draw too much current; it should be the exact opposite, they're supposed to put out a lot more light at significantly lower power. Halogens, on the other hand, can draw significantly more power.

It'd be a bit of a bummer, but I don't think that the LEDs are the cause of this, even though the change clearly triggered something.

I have to think on what, admittedly.

Good luck

gazfish

Maybe you disturbed some wiring up front when you swapped the running lights and a wire is now shorting, I’d remove the battery make sure the switch is off and then use an ohm meter to check the resistance at the bulb sockets. You’ll see some as your marker lights are wired in parallel with your running lights.
How did you manage to blow a fuse swapping bulbs? Another thought is that caused a wire to melt if the wrong fuse was in place or damaged the bulb check unit in some way.

Petza914

I swapped my 81 Euro to LED headlight and fog lights and had no issue other than figuring out which individual wires needed to go on which headlight pins since the PO had removed the plastic wire holder so all 3 wires were independent. No issues from running the LEDs.

I think your issue is related but the bulbs aren't the root of it unless you have some wires mixed up maybe at the headlights, but if your wires are in the plastic holders, unlikely.

The pod does have a metal structure that the spring clips for the switch lock onto. I would pull the end off the switch, slide out the actual switch and examine the wires that are connected to the backside of the switch. The one on the outer perimeter should be insulated vs the ones that plug into the switch more internally. Might be a good ideal to wrap around your switch with electrical tape to make sure it's not contacting anything.

Living with smoke from the switch isn't an option no matter how little.

DaveN

I did the interior festoons and most likely touched the car body while pushing them back in.
I have done this before on my 911.
Edit: Just to add the pods and fog lamp wiring are in perfect order, clean and well insulated.
I'll pull the switch today and get out the meter of doom.

Sadly, the switch pulled out of it's socket and now rests inside the gauge pod.
Guess the next days fun will be watching "Pull the Pod" videos to get the switch pluggerd back in and get better access to the offending wire(s)

Mrmerlin

NOTE make sure the battery is disconnected before you start moving the switches in and out of the pod ,
as any one of them could ground and smoke a wire back the CE panel.
once the switches are out then reconnect the battery to test

gazfish

Still shouldn’t need to pull the pod, if you remove the switch below “carefully” the two holes give you enough space to pull the socket back through with your fingers

DaveN

Had to pull the pod yesterday as the main harness that feeds the swtiches was tucked up and secured behind the cluster. Once loose I had the freedom to remove the switches with slack.
I replaced a burnt cluster illumination pot which I knew was bad and the PO had provided a spare so that wasn't it.
I put the switches back in one by one while leaving the running lights on. Noting really conclusive but I did get smoke once when putting the rear defrost switch back in.
I removed it and noticed one of the small 2 centre pins was crooked and not fully proud. Took it apart and got the pin back out and straight but it has obviously become unsecured from the plastic base. I put it back in and it seems to work, can't get any smoke yet, but I think that pin probably went back in a bit but is not shorting inside? I have found in the past the "white smoke" with no smell can be internal hot switch lubricant.
The smoke from the light switch may have been a red herring as it may have travelled inside the pod and just happen to come out that switch given it's at the top of the curvature. I did see the smoke with the light switch out once and it wasn't coming from the wiring but from the right of the wires.
Off to test it a dozen more times before I feel convinced; I'll get a new defrost switch anyway.