Disabling the dimming function?

[rich_e777]

I would like to disable the way the dash, HUD and gauge cluster bulbs dim when turning on the fog lights/headlights. However I would like to keep the incremental dimming feature of the interior courtesy lights after the car has been shut off. 

Is this possible to do? I`m studying the diagrams trying to answer my own question but coming up short.

[55trucker]

?   how short are you?.....

[rcLord510]

14 hours ago, rich_e777 said:

I would like to disable the way the dash, HUD and gauge cluster bulbs dim when turning on the fog lights/headlights. However I would like to keep the incremental dimming feature of the interior courtesy lights after the car has been shut off. 

Is this possible to do? I`m studying the diagrams trying to answer my own question but coming up short.

I’d be looking for a wire that goes from the headlight/foglight switch that goes into the bcm(you don’t clarify which vehicle, so if it’s the 94 or 95 it’ll have one) put a meter on it and see what changes on that specific wire when you flip the fog or headlight switch, I’d guess it tells the bcm to dim those components, so all together removing that wire should in theory stop that from happening, assuming that’s that wires only job. If it were me I’d put a switch in that wire and put it under the dash somewhere so I could have that dimming feature back if I liked but that’s just me…

also if it’s your tgp, it will probably be more simple since there’s no bcm, and removing that wire will almost certainly do what you’d like it to. In any case don’t just cut it in case it doesn’t do what you want it to, just depin it and remove it from the fog switch connector just for testing.

in any case, unless im missing something, this should be a very easy thing to do, just a bit of investigative work on your part. It also should not remove the incremental dimming. Those are usually on a timer and are on a complexity different part of the circuit than the dash light circuit.

Edited September 25 by rcLord510

[55trucker]

Don't know if you want to do that...the dimmer is integral in the headlight assembly, if you *at the moment* are seeing the cluster lamps *dim* when you bring on the headlamps then push up the dimmer lever to all the way bright. In that position the cluster lights won't change their brightness. If you haven't altered the wiring for the fogs they only come on when the lows are in use.

Edited September 25 by 55trucker

[rcLord510]

1 minute ago, 55trucker said:

Don't know if you want to do that...the dimmer is integral in the headlight assembly, if you *at the moment* are seeing the cluster lamps *dim* when you bring on the headlamps then push up the dimmer lever to all the way bright. In that position the cluster light won't change their brightness.

I wasn’t sure if there was a separate wire specifically for dimming under those circumstances of Turing the headlights on vs just the regular dimmer lever. If it’s one wire for all dimming on the gauge cluster and interior lights, yeah don’t.. At least in my dads 91, no matter where the dimmer is, turning on the headlights will dim all interior lights, and there’s no way to change their brightness except lower on the dimmer switch, could be different for how his 89, 94 or 95 Is but that’s how 91 cs’s are 

[Schurkey]

The point of dimming the various dash lights when the headlights are turned-on is to NOT DESTROY YOUR NIGHT VISION.

Your pupils dilate in low-light conditions.  They contract in bright light.  When you're looking out into darkness, somewhat lit by your headlights, you want your pupils dilated to bring as much light as possible onto your retinas--so you can still see where your headlights are not directly pointing--to the sides, and further down the roadway.

Bright dash lights cause your pupils to contract.  The opposite of what you want, and what is "safe".

 

 

 

Of course, you could CLEAN ALL THE DASH LIGHT LENSES, and REPLACE ALL THE BULBS WITH NEW INCANDESCENT LAMPS (direct replacement, not cheap-junk Chinese LEDs.)  I guarantee that any original incandescent light bulbs from the 1990s are worn-out even if they still "work".  You'll see that the glass "bulb" has become silvered, there's plenty of light being generated by the filament, but it doesn't get out of the darkened glass bulb.

For that matter, it's EXACTLY the same with incandescent headlights.  "New" headlights with clean, shiny, non-corroded reflectors and non-silvered glass will be brighter at the same voltage than "old" headlights.

[Black92GS]

On 9/24/2025 at 6:10 PM, rich_e777 said:

I would like to disable the way the dash, HUD and gauge cluster bulbs dim when turning on the fog lights/headlights. However I would like to keep the incremental dimming feature of the interior courtesy lights after the car has been shut off. 

Is this possible to do? I`m studying the diagrams trying to answer my own question but coming up short.

Doesn't the dimmer switch already allow this?  My Regal has a detent immediately before it turns on the interior lights where the cluster and all the displays are at full brightness. I seem to recall my 92 cutlass being the same way, as well as my parents old 97 Lumina....so I just assumed they all worked the same way. 

[rich_e777]

On 9/25/2025 at 7:03 AM, 55trucker said:

?   how short are you?.....

Depends on how many phone books I`m sitting on.

On 9/25/2025 at 5:10 PM, Schurkey said:

The point of dimming the various dash lights when the headlights are turned-on is to NOT DESTROY YOUR NIGHT VISION.

Your pupils dilate in low-light conditions.  They contract in bright light.  When you're looking out into darkness, somewhat lit by your headlights, you want your pupils dilated to bring as much light as possible onto your retinas--so you can still see where your headlights are not directly pointing--to the sides, and further down the roadway.

Bright dash lights cause your pupils to contract.  The opposite of what you want, and what is "safe".

 

 

 

Of course, you could CLEAN ALL THE DASH LIGHT LENSES, and REPLACE ALL THE BULBS WITH NEW INCANDESCENT LAMPS (direct replacement, not cheap-junk Chinese LEDs.)  I guarantee that any original incandescent light bulbs from the 1990s are worn-out even if they still "work".  You'll see that the glass "bulb" has become silvered, there's plenty of light being generated by the filament, but it doesn't get out of the darkened glass bulb.

For that matter, it's EXACTLY the same with incandescent headlights.  "New" headlights with clean, shiny, non-corroded reflectors and non-silvered glass will be brighter at the same voltage than "old" headlights.

Good point, I dont drive at night too much but might on occasions and didnt think of that. The interior lights are bright enough at night so I suppose I should be looking to add a switch for a rain/overcast mode in the circuit. New bulbs and clean lenses still don't provide sufficient light when its raining or heavy overcast skies during the daytime though. Its during times like this is when I want brighter cluster and HUD lights, not necessarily at night. The HUD is barely visible and both the Cutlass and Turbo Grand Prix instrument clusters are recessed a fair bit in and surrounded. So I`m really not trying to disable anything at all just add a switch in the right place. 

I buy Sylvania bulbs only, they make `em in Kentucky and come in every size needed. Ive yet to have one burn out.

 

 

Edited September 26 by rich_e777

[rich_e777]

On 9/25/2025 at 9:19 AM, 55trucker said:

Don't know if you want to do that...the dimmer is integral in the headlight assembly, if you *at the moment* are seeing the cluster lamps *dim* when you bring on the headlamps then push up the dimmer lever to all the way bright. In that position the cluster lights won't change their brightness. If you haven't altered the wiring for the fogs they only come on when the lows are in use.

Yes, even at full brightness on the dimmer setting the interior instrument lights dim considerably when the headlights are on. When its day time and raining or just a heavy low level cloud layer the cluster/HUD would be easier to read in a quick glance if they were brighter. Especially in Nashville driving the TGP when you have to have your eyes on every car assuming its going to do something stupid.

[Black92GS]

22 hours ago, rich_e777 said:

Yes, even at full brightness on the dimmer setting the interior instrument lights dim considerably when the headlights are on. When its day time and raining or just a heavy low level cloud layer the cluster/HUD would be easier to read in a quick glance if they were brighter. Especially in Nashville driving the TGP when you have to have your eyes on every car assuming its going to do something stupid.

Are you sure there isn’t another notch on the dimmer? Or is there a chance the dimmer switch could be defective?

I can turn everything off when the lights are on, then it goes to full backlight brightness with all of the VFDs dimmed a bit. Then there is detent that brings all of the VFDs to full brightness level. After that, you have the detent that turns on the interior lights. I know for certain my 88,89 and 92 Regal had/have this, as did my 94 Silverado. The 88 and 89 both had the digital dash, and I could run it at full brightness level when the lights were on. 

[GnatGoSplat]

All my Cutlasses had the feature where you could force it to full brightness at night, essentially overriding "night mode" with park/headlamps on.  I can't remember if the TGP was lacking that feature or not. 

[rcLord510]

On 10/7/2025 at 10:56 AM, GnatGoSplat said:

All my Cutlasses had the feature where you could force it to full brightness at night, essentially overriding "night mode" with park/headlamps on.  I can't remember if the TGP was lacking that feature or not. 

how do you do this? thats the 1 gripe with my dads 91 when i'm driving it at night

[GnatGoSplat]

41 minutes ago, rcLord510 said:

how do you do this? thats the 1 gripe with my dads 91 when i'm driving it at night

Move the slider all the way up to MAX, right before INT.  It has its own detent.

Grand Prix should have the ability too, but it says to move it to HI.

Don't have a GP any more so can't verify it's truly 100% as bright as lights-off brightness, but the Cutlass one definitely is.  That VFD is scorching bright at night.

[rcLord510]

7 hours ago, GnatGoSplat said:

Move the slider all the way up to MAX, right before INT.  It has its own detent.

Grand Prix should have the ability too, but it says to move it to HI.

Don't have a GP any more so can't verify it's truly 100% as bright as lights-off brightness, but the Cutlass one definitely is.  That VFD is scorching bright at night.

Strange, the 91 doesn’t have that… but looking at this picture from 02, it does, he must’ve put the later style headlight switch in

[GnatGoSplat]

He put the 94 style next to the instrument cluster with the knob?

I always liked the pushbutton one better looks and uniqueness-wise, but I didn't realize it was functionally superior as well.  The manual for the 94 doesn't mention having a MAX setting.  I guess they didn't think it was needed because digital dash wasn't available in 94.

[Black92GS]

7 hours ago, GnatGoSplat said:

He put the 94 style next to the instrument cluster with the knob?

I always liked the pushbutton one better looks and uniqueness-wise, but I didn't realize it was functionally superior as well.  The manual for the 94 doesn't mention having a MAX setting.  I guess they didn't think it was needed because digital dash wasn't available in 94.

It never dawned on me before THAT was the reason for the max brightness setting....but it does make a ton of sense now that I think about it. Pretty sure My 89 stayed on max brightness when I had it, as the automatic headlights kicked on before I would consider it to be dark enough to warrant turning the lights on....making the digital dash too dim on any other setting. 

[GnatGoSplat]

Yeah, some states even require headlights on when it rains, and sometimes it's still quite bright out when that happens.  Anytime I've turned on my lights during the daytime, the dash is too dim to see.

[Black92GS]

I recall seeing signs like that on a trip a number of years back.  I forget which state it was, but it was advising that it was the law that if your wipers were on, your headlights also had to be on.  Seemed strange to me....but then I remembered that our DRL laws indicate that any vehicle 1990 or new has to be so equipped, and that vehicles without DRLs (pre-1990 or US visitors) are required to have their low beams on at all times when the vehicle is in operation....so there aren't any signs indicating when the lights are to be on since they're more or less always supposed to be on. In reality though.....that last portion is rarely if ever enforced. 

The DRL rules have also changed for vehicles made after 2021.  They now need to either illuminate the tail lights with the DRLs, be equipped with automatic head-lights, or have the dash remain dark unless the headlights are on.  There has been an issue across the country with people driving at night with just their DRLs...which historically have not illuminated the taillights.  The issue was compounded by the fact that the cluster was lit up at all times, so there was no real indication to the driver about the issue. I never really understood how it could happen, as every vehicle I've owned dating back to my 89 Regal had the headlight off position double as the "auto" setting. Turns out that most imports have an actual off position as the "default" headlight switch position...and being on the turn signal stalk, it's all too easy to accidentally turn the auto lights off without realizing it.