I have an 88 Corvette and I am having a problem with the dash lights. The lights are fine during the day and I can also turn on my headlights and everything is fine , but at night when I turn on my headlights all my dash lights go out. If I turn off my headlights the dash lights come back on. Can anyone help me with this problem?

 

Check the 3 amp INST fuse.

 

I assume you are meaning the cluster ? there is a light detection cell on the dash maybe its bad?

 

I have a similar problem, but I haven't gone digging yet to find the cause. It isn't a fuse, because everything works. In my case the LCD display doesn't totally black out, but goes so dim that it can be mistaken for totally blacked out. It is unreadable. The problem isn't the photocell, because that is what is dimming the LCD display at night. Two sure fire tests of the photocell are to put your thumb over the photocell in the day light and see if the display goes dark. The other is to shine a flashlight at the photocell in the dark and see if the display brightens up as it should. Mine does, and that proves that the photocell works. In my case, the clock display in the radio goes off when I turn the parking or headlights on. I think that is an important clue that I haven't analyzed, yet. In my case I suspect an interaction problem between the headlight switch and the LCD display, possibly even a bad headlight switch. I believe the effect of ambient light should reverse between the head lights being on and being off. It doesn't on my car. I will post more as I learn more. Keep us (me) up to date with your developments.

RACE ON!!!

 

A switch contact in the headlight switch connects the dimmer control to the 4 lamps in the clutster when the parking or headlights are turned on. You could have a defective switch contact in the headlight switch.

 

That is my suspicion. When the weather warms and I can get to it, I plan to check the headlight switch outputs. I assume this is easiest done by removing the dash pad? I am more of an under the hood or drive train guy.

RACE ON!!!

 

Yes, to access the headlight switch, you need to remove the dash pad. Not hard...couple screws under the dash (I think 4) and the two next to the defogger vents. Then just lift slightly and pull out.

 

Mine does not dim or Brighten when I twist the Headlight switch.

You know what I am saying? most cars you can dim the lights by twisting the headlight switch yet nothing happens with mine.

I am thinking that this could be a potentiometer going bad on the Headlight switch...but without knowing if it works that way.....what can I say?

 

I WAS WRONG!!!

In the first response to muttley1, jfb said:After that advice, in describing my own similar problem, hoping to give and receive help, I commented:While it is true that all lights would illuminate, that was better proof of no burned out bulbs, than of no burned out fuses. It DOES indicate that not ALL the fuses are burned out. It also demonstrated that there was power to everything at one time or another. But if there were proper power to all items at the right times, there would be no problem.

I really wasn't ready to jump into this project with both feet, but because of this thread and jfb's suggestions, it was pretty easy to check the 3 amp fuse. I had checked other fuses previously, "CTSY/CLK", "GAUGES", and possibly others. I pulled the 3 amp, "INST" fuse and held it up to the light, but no cigar, the filament was unbroken. I really can't explain why, but I dug out my DVOM and installed the battery and double checked the fuse. It had infinite ohms. After twisting the fuse in the light, I could see the break in the filament. After a quick trip to the closest auto parts store I installed the new fuse. Now, the clock continues to display with the lights on and the dash doesn't seem to darken with the lights on and my thumb over the photocell. I will double check it after dark, tonight, and then it will have to pass the test of time. I am not going to spend time chasing a short on a circuit that blows a fuse only once every 24 years. If it blows again, I'll have my work cut out for me.

There are two feeds from the head light switch to the LCD instrument cluster for lighting. The first is circuit #9 from connector #4 of the head lamp switch which feeds the LCD panel directly, and the other is circuit #44 from connector #2 of the switch which feeds the fuse block and in turn powers circuit # 8 to the LCD panel through the 3 amp "INST" fuse.

jfb, thank you for your guidance.

muttley1, check your 3 amp "INST" fuse, closely.

RACE ON!!!

 

So it is the 3 amp fuse?

thanks.......always a pleasure CFI

 

Always check fuses with ohmeters, they have better eyes!

 

Last night testing mine in the dark, the LCD display doesn't brighten or dim twisting the head light switch ****. The radio, heater/AC controls, and the above console area brightens and dims through the rheostat, but not the LCD display.



It was. It works link a charm, now.



No doubt! Thanks again for the excellent guidance.

I hope all of this has been a help to the OP, muttley1. How about it? Have you got your display working yet? I didn't see a response from you after my first post. Is your display going totally dark? Or is it just going so dim that it isn't readable? I benefited from your thread and now I want to be sure we get your problem fixed, too.

RACE ON!!!

 

I would like to thank everyone for the help. This weekend i am going to dig into this and use all your ideas, some way some how i am going to get to the bottom of this and will report back on what I found. Again thank you everyone.

 

I am a little confused- should the LCD display dim when you turn the headlight ****? Mine works just like you stated? This is correct?

 

On my 89 the rheostat on the headlight **** does nothing with the headlights or driving lights off. Its only when I turn on the headlights or driving lights that the rheostat makes the cluster lighter or darker. WW

 

I think it is. However, my FSM says, "The photocell output is electrically added to the dimmer rheostat setting (if park or headlamps are ON) to determine the amount of dimming for the displays." Based on what I see, I am not convinced that statement isn't in error, but that is what is printed, verbatim. Personally, I am just pleased to have it working in the dark. It failed at the race track and it was a pain not knowing my launch temperature, and a disaster not being able to see the tach for shifting.

RACE ON!!!

 

I just had the same problem with my 89, turns out it was the fuse also. But my question is, what would cause the fuse to blow? they dont blow for no reason? And the My "inst" fuse was a 5 amp instead of a 3 so i just put a 5 back in?

 

they just get old and blow.

 

i know this is an old thread but I have the same problem in my 93, headlights on dashlights off. The difference is is if I push on the dimmer adjuster switch they will come on but if i let it go the dash lights go back out. Is the dimmer just worn out and is there a way I can fix it instead of paying 200 for another switch assy. because everything else in the switch works fine.

 

^^It's better that you bring up an old thread like this......

But you failed to mention if you checked the particular fuse....

Later...after this thread.....I had a fuse issue as well. There are strange things that occur when a single fuse is out. And these seem to be really hard to see if they are in fact blown.

I went on blind faith from what I was told on the forum...I yanked a certain fuse and replaced it....my troubles went away. But to look at the old fuse you'd swear it was still good.