Cluster/dash lighting gremlins (continued)

All previous assumptions/guesses have sucked. Here's the issue, uncluttered with crap I've already tried. My gauge lighting and other instrument panel lighting (i.e. the HVAC controls as well) has the following issue: When I first turn on the lights (either position, either parking lights or headlights), the cluster and dash lights power up momentarily; the lights then blink off and then start pulsing at a very low brightness, like the lights are starting to power up and then something cuts out. The "pulsing" is slow - a hertz, but variable, and is present when the car is running and when the car is NOT running - but only when the headlight switch is in either of the two "on" settings. If I leave the lights on and the car running, in short order I get the aroma of frying electrical stuff. I have driven British cars in the past, so I am aware of the dangers of letting all of the smoke out of the electrical system; I don't have a ready supply of German replacement smoke. There are now blown fuses anywhere in the system. My WAG is that when the car is off, some body control module keeps trying to power up the backlights, a short is detected, and the power blinks back off. I have not yet Durametricked the car; I'm assuming that will be a strike out, but stranger things have happened. The pulsing is the only thing I would even remotely consider a "clue," but I have no idea if it's actually worthwhile or yet another red herring.

Whatever you do, don't feed it after 7pm. That makes gremlins grow.

Switch or voltage regulator.

Gonna order the voltage regulator - I don't think it's the cause, but isn't one of the things you don't think it is ALWAYS the cause?

I might have missed it in the previous post but do the headlights/taillights/non-pumpkins flicker as well?

Litronics? Just wondering if one of the igniters is firing then dropping the load or shorting enough to cause a pulse as it tries to refire. I also thought that maybe removing both L/R headlights and while it is running turn the headlight switch on. Then does it still do it?

Interesting that smoke smell only occurs with engine running? Could the increased voltage/current from the alternator with engine running be comprising a loose/weak connection? Maybe behind the fuse panel in the drivers footwell? Did you ever stick your head under the dash for the good look you had mentioned? I assume yes.

Yes, I've done a fair amount of troubleshooting, including checking as much under-dash wiring as possible, checking the three harnesses (plus the harness for the hazard switch) in the instrument cluster, pulling the cluster apart (before I realized the HVAC unit was involved, I was treating this as an instrument cluster issue. Stupidly.). The voltage never peaks above 14 with the engine running, it's fully changed (~12v) when the engine is not running. The pulsing I noted is ONLY visible in the cluster/HVAC backlighting - not in the litronics or any of the other visible lights. That the pulse is visible both with the car running and not made me wonder if there if the dimmer circuit is acting up, but I don't know a way to isolate that yet. I ran out of time last night; the plan was to disconnect the Litronics and my LED taillights to eliminate both as possible suspects. Keep the ideas coming. SOmething is going to be the correct answer...

How about the dash light dimmer ****? Not sure what is behind there on the cluster board but maybe a bad resistor or something like that? Maybe it's like a little rheostat. Any signs of something on or near the cluster dimmer maybe burned? Does the dimmer work?

Does it do this key on or key off? Or always?

Clearly...you did not kill the mice...

Quotes source post: 14354461

Key on, key off, motor running. If the lights are on, it does it. After the initial "normal" period of illumination, which lasts from a couple hundred MS to a few seconds, it blinks off, then starts the low-power off-on "blinking"...

How about my dimmer idea? Does the dimmer work? It is a point of commonality between the cluster and HVAC screen. Do you have the standard bulbs in the cluster or LED's? Might be a voltage issue with LED's.

The dimmer is on my short list of suspects; I need to look at a schematic to figure out the simplest way to defeat it.

Out of curiosity, I checked the wiring diagram for you and here's my conclusion: The light switch (when turned to parking light or higher) supplies +12v to term58 (white plug pin 14) of the cluster. The cluster supplies power to the interior accessory light bulbs (e.g,. radio lights) on blue socket pin 11. The cluster supplies power to the LEDs of the interior switches (e.g., rear defroster) on blue socket pin 10. I can't find the cluster dimmer on any wiring diagram. I think if you can disconnect the wires one by one from those output pins on the blue socket, you may be able to isolate which circuit is overloading the cluster (assuming that's the problem).

Thanks, Ahsai. Yesterday, I sat in a 100+ degree hot car with the lights intentionally on (and presumably making something melt and try to catch on fire), but I was able to see precisely where the smoke's coming from; it's either the leftmost connector or there is a chafed wire in the dash right behind that connector. With the info you provided and a really good idea of the physical location, I'm hopeful I'll be able to nail this down when I get back on Sunday. Thanks for the ideas and comments; this one has been a grind, but I'm feeling pretty good about this one. As an aside, my blinking stoplight module was not related, but I think it _was_ the cause of my few remaining (once every other month or less often) ABS/PSM warning lights. I also noticed a pronounced increase in alternator noise on AM stations a few months ago, but there was no equipment change. I thought at the time I was just imagining it, but now I'm fully expecting to find a chafed wire harness with at least one wire grounding out.

Just have some water handy to put out the fire p.s. It has been a long while since I've had the headlights out, but the last time I did I noticed plenty of wire insulation gone. Really. A bunch of bare wires. Ummm...did not replace or repair but figured I would have to at some point in time. So apparently with the age our cars are getting, the wire insulation is breaking down. MOF 1Million79 to add to the list. And AM? Really? Does anybody listen to AM anymore? Nothing but religious and rabid local talk show hosts on medical issues.....

Thanks, Joe. I pulled the frunk liner a couple of days ago in preparation to disconnect the litronics, but I didn't specifically because the insulation is currently NOT all cracked, and I wanted to avoid d*cking with it if at all possible... At this point I need to throttle back the whole "let's mess with everything" urges. Every connector I touch or wire I bend has the potential to need fixing, so I need to be a little less hamfisted...

Yeah...from what I saw INSIDE the headlight...I don't even want to think about the places we don't normally go. Age is a strange thing. Beginning to wonder about my own age. Damn wiring...

May want to check the a/c ripple of your alternator for the increased AM noise. Could be some diodes going bad.

Turns out that one of the contacts in the side marker that initally got nailed by road debris was pushed down into the body of the connector and was shorting in a place that wasn't visible without taking a proper look at it. This short wasn't enough to blow a fuse...but plenty to make the instrument cluster smoke and not work right with the lights turned on.