Dash and Guage lighting question
Thread Starter
Instructor
Joined: Oct 2007
Posts: 214
Likes: 0
Dash and Guage lighting question
This is probably a silly question...
Shouldn't the instrument cluster illuminate even when the running and headlights are off?
I rarely drive our Z but when I do it seems like the cluster is entirely too dark unless I turn on the lights.
If it's supposed to illuminate, any suggestion as to where to start troubleshooting?
Shouldn't the instrument cluster illuminate even when the running and headlights are off?
I rarely drive our Z but when I do it seems like the cluster is entirely too dark unless I turn on the lights.
If it's supposed to illuminate, any suggestion as to where to start troubleshooting?
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Most of the cluster lighting is accomplished with the use of DAY GLOW Paint and black lights. In each out side corner of the cluster are a single 4" long BLACK LIGHT florescent tube. The black light should come on when you unlock the car with the FOB. If you bend down and look at the cluster at an extreme angle, you can see the right side tube pretty easy. See if they are working. They operate on an INVERTER that takes 12 VDC and turns it into 700 VAC.
Some of the face back lights operate on 12 VDC incandescent bulbs and get brighter and dimmer automatically from the interior light sensor on the right side of the cluster. In bright sunlight the cluster should get brighter on its own. You should also make sure that the manual light level sensor is not turned all the way down. Press the button in so the pops out and rotate it clock wise. If you turn it FULLY CLOCK WISE it will turn the interior overhead light on ALL THE TIME!
Some of the face back lights operate on 12 VDC incandescent bulbs and get brighter and dimmer automatically from the interior light sensor on the right side of the cluster. In bright sunlight the cluster should get brighter on its own. You should also make sure that the manual light level sensor is not turned all the way down. Press the button in so the pops out and rotate it clock wise. If you turn it FULLY CLOCK WISE it will turn the interior overhead light on ALL THE TIME!
Thread Starter
Instructor
Joined: Oct 2007
Posts: 214
Likes: 0
Thanks for the input Bill.
Looks like the black light bulb circuit is not working. I can see the right side light location you described and there's no visible light at all. Turning the dash dimmer up makes no difference at all but turns on the interior lights in the rear view mirror. Turning on the running lights will illuminate the dash from the rear and I can see a little light bleed or reflection in the area where the black light bulb is. Turn the running lights off it's all black.
I guess it's time to troubleshoot the 700VAC circuit. Thanks!
Looks like the black light bulb circuit is not working. I can see the right side light location you described and there's no visible light at all. Turning the dash dimmer up makes no difference at all but turns on the interior lights in the rear view mirror. Turning on the running lights will illuminate the dash from the rear and I can see a little light bleed or reflection in the area where the black light bulb is. Turn the running lights off it's all black.
I guess it's time to troubleshoot the 700VAC circuit. Thanks!
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
That module has been known to burn up. They dont sell the module so,,, you will need a new cluster or a used cluster that you can part out. The module comes out and can be opened. The transistors burn up.
Let us know what you find..
Here are a few post to help you with the disassembly and inside componet ID.
- C5 Gage Cluster disassembly - http://forums.corvetteforum.com/c5-t...post1570380674
- C5 Gage Cluster Post - http://forums.corvetteforum.com/c5-t...post1570380878
Bill
Let us know what you find..
Here are a few post to help you with the disassembly and inside componet ID.
- C5 Gage Cluster disassembly - http://forums.corvetteforum.com/c5-t...post1570380674
- C5 Gage Cluster Post - http://forums.corvetteforum.com/c5-t...post1570380878
Bill
Thread Starter
Instructor
Joined: Oct 2007
Posts: 214
Likes: 0
Looks like I've made a breakthrough.
Looks like I have a flaky dimmer switch. Dash lights even with the headlights on wasn't working earlier either. Fiddling with the **** I eventually got the backlights to work intermittently, and interestingly the black lights started working. The backlight control is not very linear at the moment, so I'm suspecting dirty contacts.
Not sure if the switch is fixable but I'll see sooner than later. Hopefully a switch is available still if not.
Looks like I have a flaky dimmer switch. Dash lights even with the headlights on wasn't working earlier either. Fiddling with the **** I eventually got the backlights to work intermittently, and interestingly the black lights started working. The backlight control is not very linear at the moment, so I'm suspecting dirty contacts.
Not sure if the switch is fixable but I'll see sooner than later. Hopefully a switch is available still if not.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Instructor
Joined: Oct 2007
Posts: 214
Likes: 0
Hey Bill, Interesting you say that. That's what I had been doing.
I was sitting in the car warming it up when leaving work. The sun was low in the sky and gauges were dark. I turned on the parking lights and the only change was the MPH lit up. I figured the dimmer was down too low but it was already up near max. So I just started twisting it back and forth and saw a slight flicker of the back lighting... I did this a few more times and the backlights came on and stayed on. Nice. So I pushed the **** back in and they went out. Doh! I repeated the effort and couldn't get the backlights on again. So I headed out... a few miles down the road I noticed they were back. Still talking back lights here.
On the way home I goosed it getting on the freeway and the car thanked me by lighting the Check Engine Light. sigh... Got home and brought up the DIC then realized I still had dash lighting even after I had turned off the headlights. Sweet!
I'll give it some additional twisting and fiddling to see if I can get the lights to be consistent.
Next on the list is figuring out why I'm throwing P0172 and P0175 codes (second time in 2 days). Always after fairly moderate acceleration... probably need another thread, will see.
I was sitting in the car warming it up when leaving work. The sun was low in the sky and gauges were dark. I turned on the parking lights and the only change was the MPH lit up. I figured the dimmer was down too low but it was already up near max. So I just started twisting it back and forth and saw a slight flicker of the back lighting... I did this a few more times and the backlights came on and stayed on. Nice. So I pushed the **** back in and they went out. Doh! I repeated the effort and couldn't get the backlights on again. So I headed out... a few miles down the road I noticed they were back. Still talking back lights here.
On the way home I goosed it getting on the freeway and the car thanked me by lighting the Check Engine Light. sigh... Got home and brought up the DIC then realized I still had dash lighting even after I had turned off the headlights. Sweet!
I'll give it some additional twisting and fiddling to see if I can get the lights to be consistent.
Next on the list is figuring out why I'm throwing P0172 and P0175 codes (second time in 2 days). Always after fairly moderate acceleration... probably need another thread, will see.
Safety Car
Joined: Dec 2011
Posts: 4,704
Likes: 239
From: Redondo Beach CA
Thanks for the good info, I didn't know how the lights worked, but should have learned by now that my old lightbulb in a hole mental picture was outdated and would be shunned by GM because of the low potential to drive owners insane over time.
If it helps, from my time spent among the audiophiles, a **** that uses a wiper on a resistance coil is best cleaned with WD 40 instead of electrical contact cleaner. I have a volume control **** that was noisy and I had cleaned it twice with electrical cleaner over the years. On posted advice, I switched to wd40 and the **** has been quiet ever since.
I now have useful information about productive side jobs, (fresh inverter, bulbs maybe) when I ever get around to fixing my heads up display mirror pivot.
If it helps, from my time spent among the audiophiles, a **** that uses a wiper on a resistance coil is best cleaned with WD 40 instead of electrical contact cleaner. I have a volume control **** that was noisy and I had cleaned it twice with electrical cleaner over the years. On posted advice, I switched to wd40 and the **** has been quiet ever since.
I now have useful information about productive side jobs, (fresh inverter, bulbs maybe) when I ever get around to fixing my heads up display mirror pivot.
Thread Starter
Instructor
Joined: Oct 2007
Posts: 214
Likes: 0
"Scratchy" potentiometers... I know that sound well. 
I've never tried cleaning one with wd40, I'll keep it in mind next time.
Maybe someone who has messed with the dimmer switch in the past may know, but I believe the module is a sealed unit.
That said.... Spent some time reading the FSM and never considered that the only way to get to this potentiometer is to pull the entire dash apart. Crap. I'm sure you realize that if you're looking into accessing the HUD assembly.
Looks like I'll be doing a lot of twisting and fiddling as Bill suggested.
Just for fun... here's a pic of the black light.
I've never tried cleaning one with wd40, I'll keep it in mind next time.Maybe someone who has messed with the dimmer switch in the past may know, but I believe the module is a sealed unit.
That said.... Spent some time reading the FSM and never considered that the only way to get to this potentiometer is to pull the entire dash apart. Crap. I'm sure you realize that if you're looking into accessing the HUD assembly.
Looks like I'll be doing a lot of twisting and fiddling as Bill suggested.
Just for fun... here's a pic of the black light.