I did a search, but found nothing about this. There are times when my speedo dims, whether it's daytime or night. At night it gets almost too dim to read. It is too dim to safely read. The lights anywhere else on the dash appear to stay the same brightness. It's just the middle section with the speedo, fuel gauge, etc. are located. The tach stays well lit. I have a '91 auto with aftermarket stereo and alarm. The sys light has been flashing since I got the car in December. The interior lights were stuck on due to bad switch in driver's door. That has been fixed. Hope I listed all info needed to help solve this issue.

 

You probially have a ground problem. Try removing them and clean them and then replace them. Keep each ground on the lug you take it off of so you will not get cross talk.

 

Sounds like a job for my mechanic. I don't have the experience to do that.

 

I have the same issues with my '91 coupe. First, don't get too excited aobut the "SYS" light. GM did not allow for the fact that thier BOSE units would turn out to be junk, and any common aftermarket radio will not have "feed" to tell the SYS system that the radio is OK.
As for dimming speedo light - it's annoying as all get out. I have yet to figure out how to cure the problem. I think it may be related to the dimmer, as there have been times when I can play with the dimmer and get the speedo light to respond. But not always.
I also keep arriving back at a "ground" problem, but I do not know where these lights are grounded, hence I haven't been able to check if the ground is lose or dirty.
If you find out where the lights are grounded, kindly let the rest of us know.
Glen

 

I haven't been concerned with the SYS light after reading about it here. As for fixing the speedo light, if I figure it out, I will share.

 

There are four lights that backlight your cluster. Each lamp slides into a socket that comes through the back of the rear (closest to driver) circuit board (there are two boards). These sockets bayonet (turn and stop) into a hole in the circuit board and two spring ears make connection to copper pads on the circuit board. These lamps are quartz halogen and are very hot and this heat oxidizes the spring ears and copper pads on the circuit board and this makes an intermittent or poor electrical connection which makes that particular (speedo in your case) lamp go dim or out. You need a new socket or the connections cleaned up.

 

Thanks for the info. I will get it to my mechanic so if he breaks something, he can pay for it.

 

I will check that mine (93) does the same thing

 

I have the same problem with my '90. seems to only happen durring the day though. If my headlights are on the spedo dosen't dim unless I use the dimmer switch. It's been driving me crazy! !

 

Mine does the same thing, although its just one of the bulbs. Its actually VERY easy to replace and could save you quite a bit of money doing it yourself. Don't be afraid to get in there.

Theres like 6? screws that hold the dash panel on around the gauges.

Press the springclip holding the headlight **** onto the shaft and while pressing it (which a small screwdriver) pull it off the shaft.

Move the steering wheel tilt all the way down into your lap, then unscrew the lever out of the steering column. Pull the dash panel out.

You will immediately see 4 metal plates about the size of quarters...these cover the light bulbs in question. Just pull the headlight switch on and find out which one is loose, you can sometimes tap on the lights or around the panel to find the loose lights. Becareful not to tap too hard as al lthe gauges are LCD and you could crack one (don't be afraid of it, just don't go hitting it hard with anything)

once you find the light in question, pull the metal cover off the top of it, then get the bulb out (big PITA to get your fingers in there or something in there to pull it out)... simply replace it with one from the auto parts store, or if the light is still good, clean out the contacts where that bulb sits.. then reseat it firmly.

You can leave the dash panel off and go drive around for the day... if it doesnt do it again, it may have just been a loose connection. If it still does it, the bulb may need to be replaced (try swapping lights with another one and see if the problem follows the bulb in question). Bulbs are only a couple bucks at any auto parts store.

I replaced all mine with red once, all the gauges were a cool blood red color.