Are the HVAC buttons supposed to illuminate when you turn on the lights? There is an indicating light above each button that illuminates to indicate which function is in use.

 

There is back lighting for all the labels. Also the digital display lights up. The power for the back lighting comes from the radio, so if you have an aftermarket radio it might not be available. It's source is the dash and is controlled by the headlight switch and the back lighting photocell.

 

Thank you for the reply. The radio is factory original. Unfortunately, the backlight for the HVAC buttons do not light, only the indicators above the buttons light up, again only the ones that are in use at the moment. Anyone have any ideas why all those lights may be out?

 

It may be as simple as burnt out bulbs. I just bought a '97 Tahoe and 7 of the 11 dash bulbs were burnt out.

Good luck!

 

Assuming the radio back lights dim as expected, it sounds like a problem with the connection between the radio and HVAC control head.

 

My '94 has a after market 6 CD player added since the factory CD quit.
Could this affect the back lights of the non working radio, HVAC, and dash?? I've just owned this a couple months and still sorting out the OP issues.

 

How can this be corrected??

 

Cliff are you still on here - you seem to have a lot of good answers on here.

 

There is a single wire connection between the radio and the HVAC control panel. It plugs in to the back of the HVAC control head.

 

I had the HVAC out a couple weeks ago - didn't notice any loose wires but wasn't looking either - would this wire control the back lights to the HVAC and the radio - neither are working - to simplify all the back lights right of the steering wheel does not work when the head light switch is used - the photo cell sensor does not light up the dash as it should in the daytime either - could this be related - my car is a '94 - thanks for the info.

 

Hello,
I am just finishing up a clean up and new stereo install in a 1988 Coupe. Some of my dash board lights were not working and the power to my AC control box was intermittent at best. The AC kept flashing as I hit bumps or if I tapped the dashboard from the bottom.
My problem was due to a faulty ground and other electrical woes but primarily corrosion. I went through the dash with a meter reading the voltages. I found that my dash was seeing 9-10 volts max, my AC control box even less. I started cleaning every connection starting with the Digital dash and working my way to the right. I also replaced the Headlight switch just to be safe as there was no change when I dialed the previous headlight rheostat around.
There is a post where the 12 volt + (HOT) wires all meet the battery voltage. It is right behind the battery. I started there and cleaned every terminal I could reach. After reassembling my dashboard I found that my digital dash was back to its full brightness and works great. I had been afraid that my digital dash was shot and needed a rebuild.
While doing this work I replaced every light bulb in the dash. I even took the digital dash apart to access the bulbs and their connections better. I don't want to have to remove the whole dashboard again for as while so no used bulbs were used. I found all the bulbs at my local NAPA dealer, but some of them are not cheap.

I use a lead pencil with an eraser to clean my connections. The eraser is one of the best cleaners I have ever used. It removes the oxidation on the copper and doesn't have anything caustic about it. I used it on every connection that I could reach safely.
Then I went thru every fuse and checked for voltage drop with my meter, it was alarming at how many had enough corrosion to make problems. I had fuses that had not blown but made no electrical connection. I replaced them and cleaned the fuse block connections as well.

My cars AC does not have anything but the one connector (~15+ pins) on it. I have not seen where another wire could plug into it. It is however a 1988 with the optional AC control unit. It is all digital.

You sound handy enough to be able to dig around with a good Fluke Volt Ohm Meter. I suspect that you are experiencing a bad connection somewhere. Just follow the wiring and you will find it. The factory Service manuals are invaluable here in this work, especially the wiring addendum that was available for my year. The Digital Dash Repair Book is another valuable resource.
I wish you the best of luck!