the instrument lights start off on,when you start the car, with all of the lights on when you put the headlights on. After a minute, they go off, but the headlights stay on and ironically, the radio tuner light gets bright. While the instrument lights are on you can dim and brighten them using the dimmer switch. I have replaced the light switch, inspected the dimmer switch, and the fuse is fine since all of the lights do work when you first. What else can be done to solve this problem. My volvo tech tells me I may have to replace the instrument cluster with an old one from the junk yard. I am trying to prevent having to spend a bunch of money to do a ground trace etc. Any ideas. Thanks in advance

 

light sensor? Not sure...

 

I had the same problem and it was my dimmer switch.

 

Even though the dimmer switch looks good, I'm betting it is the culprit

 

Let us know if the dimmer switch fixes the issue.

 

I would put my 2 cents for dimmer switch or the headlight switch.

 

Get a schematic for the car, the instrument lights must go through the dimmer. My electrical experience says that the dimmer winding is heating up and opening. Once it does that the voltage to the radio lighting INCREASES due to the lower current draw on the circuit. Replace the dimmer or temp bypass it if they stay on it's the dimmer.

 

Had same problem, changed dimmer and prob was gone.