Gauge Lighting

Briann1177

Goblin Guru
Is the back lighting for instrument panel gauges supposed to work? The driver information center LEDs get brighter/dimmer depending on headlight settings, but everything else is dark.

I have a hunch, but I'd like to confirm it.
 

Briann1177

Goblin Guru
If it's the dark green and purple for the dimmer switch, I originally had them soldered together. Nothing. I cut them and still nothing.

So it sounds like gauge lighting is supposed to work?
 

JSATX

Goblin Guru
I found my answer. I even asked this before and Lonny said the dimmer wires need to be soldered together.
What are you referring to? Mine have always been really dim but I still have the dimmer switch plugged in. It works it’s just not bright Enough
 

Briann1177

Goblin Guru
I think I know what the problem is. I'm pretty sure I don't have my brown tail light wires hooked up in the back. I'm going to be inserting a connector back there so I can plug into the trailer connector on the back of my truck, and I don't think I ever hooked those two ends up. One of those brown wires feeds the BCM and controls the instrument panel back lighting.

Will check after work.
 

Briann1177

Goblin Guru
Chalk this one up to a bone headed mistake. I hooked the wires up, and the gauge lighting came right right on.

On a side note, I don't think the dimmer wires do anything other than give you some tiny sparks when touched together. Whether they're shorted together or left open, the intensity seems to stay the same. I think I'll just leave them snipped.
 
So this should be a variable resistor where open gives you one brightness and short should give you the opposite brightness.
Looking @ the schematic I'm surprised you get sparks but snipped seems like a reasonable option.
Maybe you can give 12v to the instrument panel lights if you can find those wires.
 

Briann1177

Goblin Guru
I don't think that circuit is designed to be shorted together like that. I think the lower resistance on the dimmer knob is 25 ohms and the upper range is around 5k if I remember right.
 

ctuinstra

Goblin Guru
Chalk this one up to a bone headed mistake. I hooked the wires up, and the gauge lighting came right right on.

On a side note, I don't think the dimmer wires do anything other than give you some tiny sparks when touched together. Whether they're shorted together or left open, the intensity seems to stay the same. I think I'll just leave them snipped.
Hooked up what wires, the brown tail light wires? That doesn't make sense why it would feed through those and then back the BCM. Most of them are joined together at a junction and then fed to all of the lights if I'm not mistaken.
 

Briann1177

Goblin Guru
Yes. In the '09s, one of the brown wires in that junction runs to the BCM. The instrument panel back lighting is controlled by the parking light relay.
 

lksohm

Well-Known Member
I'm bringing this topic back from an old grave.
I have no instrument back lighting. I have what I think is the dimmer wires connected. These terminate at "Instrument Panel Lamp Dimmer Switch Signal" pin 26, and "Low Reference" pin 58.
Neither my speedo/tach guage or boost guage have light so I think it is signal related.
All of my other lights work as they should(head, tail, indicators...). Is there somewhere I can probe to test the signal?
Thanks!
Edit: my auto light sensor doesn't seem to do anything. I doubt that's related.
 

lksohm

Well-Known Member
Update:
I found this posting

I'm not sure if a LSJ car would be the same as this LNF info but I don't seem to be getting any voltage from the grey wire that should signal the backlight.
How bad of an idea would it be to feed 12V into that pin into the cluster?
 

ctuinstra

Goblin Guru
Update:
I found this posting

I'm not sure if a LSJ car would be the same as this LNF info but I don't seem to be getting any voltage from the grey wire that should signal the backlight.
How bad of an idea would it be to feed 12V into that pin into the cluster?
If you aren’t getting the 12v on the gray wire, you could cut it and feed 12v from the accessory circuit directly into the dash at that point. It won’t cause any other issues. That is only for the lamps, nothing else.
 

lksohm

Well-Known Member
I triple checked all the fuses in the BCM with no luck on the culprit.
I cut the gray wire going into the cluster and fed in 12V. The gauges lit up. I did the same thing with the boost gauge and it lit up as well.
I decided that it wasn't worth fighting to find the root cause of the issue any more and pulled power from the keyed power source on the boost gauge to get the backlights working.
Man, I sure see why you swapped in better LEDs into your cluster. I can't believe the lights are this dim in a production cobalt.

Thanks for helping me out guys!
 
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