Cluster/dash lighting gremlins (continued)
07-27-2017, 01:29 PM
#1
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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.
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.
07-27-2017, 02:14 PM
#4
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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?
07-27-2017, 02:34 PM
#6
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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?
07-27-2017, 02:45 PM
#7
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.
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07-27-2017, 03:20 PM
#8
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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...
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...
07-27-2017, 03:40 PM
#9
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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?
Last edited by DBJoe996; 07-27-2017 at 03:58 PM.
07-27-2017, 04:39 PM
#12
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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"...
07-27-2017, 04:54 PM
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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.
07-27-2017, 07:06 PM
#15
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).
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).