John in RI

iTrader: (167)

How does the instrument panel / console back-lighting work in YOUR Digital Dash Trans Am / GTA ??

I thought I had a electrical problem but after reviewing the shop manual I think I might be dealing with a design flaw. I found that my 88 GTA was not properly illuminating the instrument and console lighting as it should. ( the lighting behind the buttons, in the heater control, console bezel, ect.. ) The backlighting would not work under any circumstance.

I began messing around under the dash and after replacing the Firebird "remote dimmer" I got the panel backlighting functional again - but in a limited way. I also swapped about 1/2 dozen or so headlight switches onto the dash just in case that was causing my "issue" but there was no change in the way it's working: Probed th wiring for voltage and found nothing problematic.

Scenario 1:
Get in the car and turn the key to RUN.
Cluster lights up, backlighting is off.
Turn on the PARK or Headlights; panel lights illuminate and the dimmer is functional.
* works fine

Scenario 2:
Get in the car and DO NOT turn the key to RUN.
Turn on the PARK or Headlights; panel lights DO NOT illuminate
* This seems like a problem to me. All the exterior parking lights function as they should but the instrument panel and console lights are not lit up. When performing the same operation in a Camaro, the dash/console lights become active WHEN-EVER the park/ headlights are turned on,..... even if the key is not turned to RUN.

Scenario 3:
Turn the key to accessory
- Radio display works and radio turns on.
Turn on the PARK or headlights
- Radio display goes dark - radio keeps playing, no backlighting.
* This seems like (the same) problem to me. These steps tell me that the light switch IS sending a "lights on" signal from the Light switch to the radio ( Brown Wire ) but there is no voltage being supplied thru the dimmer circuit ( Grey wire )


When I checked the shop manual ( all I have now is an 86, not 88 like my car) I found that the INST fuse ( feeding the Remote dimmer ) only seems to gets power when the key is in RUN/START/BULB test. So; seems like if the key is OFF the panel/console lights will not work - even if the PARK or headlights are turned on.

IS THIS HOW YOUR DIGITAL DASH WORKS ??


Here is the wiring schematic for an Analog dash: The red line shows how the rheostat dimmer gets it's power directly from the 'TAIL' fuse ( Hot at all times.) This means the rheostat can control the backlighting as soon as the headlights are turned on.




Here is the wiring schematic for the digital cars. You can see that the Rheostat dimmer gets it's power from the 'GAUGE'S ( hot in RUN TEST AND START only ). Since it only gets it's power if the key is turned - the rheostat is never active if the key isn't turned.


POSSIBLE CORRECTION TO DESIGN FLAW


Because the GAUGES fuse sends power thru about a dozen other pink/black "switched power" accessories I can't simply splice A feed from the Brown headlight signal wire to the Rheostat "IN" because then all those devises will get power full time. I think that by cutting the rheostat from that GAUGES circuit completely (green line) and then splicing the brown wire to ONLY the Rheostat "IN" pin (Blue line) I should force the backlighting to function the way I want it to.

I want to be able to turn on the PARK or Headlights while sitting in the car (with the key in my pocket) and I want the Insrument panel / radio/ center console backlighting to illuminate.

It will be awhile before I can test the wiring and the theory, but I think this will work.

Input from the digital dash crowd ??

86White_T/A305

I dont have the digi dash but your theory sounds ok.Do you have a stock radio or is it changed to aftermarket? Sometimes people wire the dimmer/illumination wire wrong behind there and cause problems but I dont know for sure if the digi dash is supposed to function this way..or illuminate like the analog dash does with the key off and lights on.

John in RI

iTrader: (167)

Thanx for the input on the radio,...... I can't count how many times I've had to re-work someone's custom radio installation to resolve problems they have caused !! In this case The radio was aftermarket but it was properly wired, then removed, then a sock radio was re-installed.

It might also be worth mentioning that all of the cars exterior lighting appears to function normally.

It really seems like the system was designed not to work in the digital Firebirds as it does in other cars because the only time the Remote Dimmer can function is when the key is in the ignition and turned to Run, Start, or Bulb test. Even if the idea was to only allow the IP backlighting to operate if the key is in the ignition; it's not even wired to work 'properly' when the key is turned back to ACCESSORY.

John in RI

iTrader: (167)

BUMP

Anyone else own a Digital Dash Trans Am / GTA ??

rawley2

Scenario 1 and 2 are working correctly. I was going to fix my accessory switch today but its been raining all day. That was why I did not answer right away. LOL

If you give me a chance in the morning I will have the accessory working and will know about #3.

I screwed up the other day installing my column and its binding and will not go to the accessory part of the switch. Bet its hitting a wire or something.

Anyway I will know tomorrow..

rawley2

I read your #3 wrong. I will check that out again in the morning.

rawley2

Ok number 3 works like you said unless I start the car then I can control the radio lights with the dimmer.

Jeffs82TA

iTrader: (1)

does it have a light sensor like corvettes have? My vette digiatl stuff brightens or lightens depending on how shaded the inside is.

rawley2

No they do not. I have 2 digital dashes. I had to change the card for the tach so I have had them stripped to the bones. Nothing in there like that.

Now I have one digital dash and a box of digital dash parts. LOL Keeping them in case something else happens to it.

The way mine works seems normal to me. If you turn the lights on the dimmer takes over. If it's real bright outside it may seem dim I guess.

John in RI

iTrader: (167)

rawley2,....

When you say they "work" Does that mean your car operates as I described ??

In senario 2 & 3 I would consider those outcomers a design flaw. I say that because the dash illumination does not work - unless the key is turned to RUN.

Another quick question;

My digital dash Berlinetta has a odometer chip that can be swapped from cluster to cluster ifthe cluster gets swapped to retian the correct odometer reading. Does the Digital Trans Am dash have am "odometer chip" too ?? What was the reason you swapped the tach card ??

* Thanx in advance !

rawley2

I swapped the card because the tach was reading about 2000 rpm high.

Here is the card from the odometer. If I remember correctly this had 181,000 roughly when I tested it. My car has 58,000 on it so I used my card for it. LOL

Anyway I think the chip your talking about is the one with the clip.

Sorry for the dust it's been sitting on the top shelf in my garage.. Also a crummy cell phone pic.

rawley2

It does exactly like you described.

I don't really see a problem with 2.

Now with 3 and the display going out on the radio I think is weird but I have gotten used to it I guess. I don't normally sit there with my lights on, listening to the radio, with the engine off.

John in RI

iTrader: (167)

Thanx for the info !

This is the first car that I can remember sitting in where the Panel illumination didn't work when the car was off. Just seemed strange to me - but it appears as if it was designed that way for some reason.

Once I get my GTA back in shape I'll be sure to post here with an update to report back if my "fix" works as I hope it will.

P.S. That might take awhile !

rawley2

I have to know. Is that the mileage chip?

I did a mod to my dash to hide the shift light. I am thinking once I get my engine built I will put one in it. The auto does not have a shift light but it does have the box for it and it looked tacky. Plus it's not actually in there to work. That was a "for sure" design flaw. LOL

Mine will look like yours soon. I am rebuilding the suspension and then it's time for a 383 or a 406.

EDIT: I will tell you the color was off on the dash glass on the car with more miles. SO maybe they do not light to keep your dash from fading to fast. The dash with more miles is more orange and mine is more blue when looking through the LCD glass. May want to keep that in mind.

John in RI

iTrader: (167)

Yes,... I believe it is. It looks EXACTLY like the odometer chip I'm familiar with from the Digital Berlinetta clusters. As a matter of fact - they look so much alike I'm willing to bet they are interchangeable.

John in RI

iTrader: (167)

The GTA Digital dash odometer chip is NOT the same as the Berlinetta Odometer chip. The GTA Chip is larger and they do not interchange.

alex722607

iTrader: (3)

I actually had the same problem that you did John. Mine actually resolved itself when I replaced the dimmer switch. But all in all I had the same exact problem, no interior panel backlighting and it sucked driving at night. -- And yea -- I have a digital dash. At first I thought it was the remote dimmer too, but it wasn't. I found the dimmer switch at rockauto, brand new. Problem solved

88gtadan

my dash was giving me back lighting issues for weeks and turns out that my altenator wasnt charging either .... bad fuse under the dash

Firechicken86

iTrader: (1)

Does anyone know what the lightbulb on the board that houses the tachs for water, oil and voltage is for? I've had two digital dashes and that bulb never wants to illuminate. Also, on the bottom left (dash facing you) there is an empty housing for a bulb to go into. What is that for? sorry to hijack the thread

Bob88GTA

iTrader: (2)

Old Thread, I know. I bought this car new in 88. No hack wiring, original Digital Dash
Scenario 1:
Get in the car and turn the key to RUN. MY DIMMER WORKS IN THIS SCENARIO
Cluster lights up, backlighting is off. MINE IS ON
Turn on the PARK or Headlights; panel lights illuminate and the dimmer is functional.
* works fine

Scenario 2:
Get in the car and DO NOT turn the key to RUN.
Turn on the PARK or Headlights; panel lights DO NOT illuminate SAME AS MINE
* This seems like a problem to me. All the exterior parking lights function as they should but the instrument panel and console lights are not lit up. When performing the same operation in a Camaro, the dash/console lights become active WHEN-EVER the park/ headlights are turned on,..... even if the key is not turned to RUN.

Scenario 3:
Turn the key to accessory
- Radio display works and radio turns on.
Turn on the PARK or headlights
- Radio display goes dark - radio keeps playing, no backlighting. SAME AS MINE
* This seems like (the same) problem to me. These steps tell me that the light switch IS sending a "lights on" signal from the Light switch to the radio ( Brown Wire ) but there is no voltage being supplied thru the dimmer circuit ( Grey wire )

scoflaw

iTrader: (2)

I have an unmolested 88 gta digital dash,

#1 just like Bobs

#2 same

#3 radio display works and turns on.
turn on lights , backlighting lights everything up except digital dash. Dimmer wheel has no effect at this time.