This 2000 GMC Jimmy came in with the complaint of no dash lights at night. This is actually pretty easy to test and repair. First turn the park lights on and check to make sure the exterior park/tail lights are working. These were on this vehicle.
Next check for power on the ILLUM fuse in the driver’s side interior fuse box. The panel dimming switch needs to be at full brightness during testing. If it is turned all of the way down the fuse will appear to have no power. Before actually replacing the switch you should check to see if the park lights are working. If they are also not working check the 20 amp PARK LP fuse in the underhood fuse box. If there is power on the ILLUM fuse place the truck in a dark location or use a blanket to cover the dash. Then check all of the bulbs for operation. If there are any illumination bulbs on the problem is not the switch the problem is blown bulbs.
The list of illuminated devices include the instrument cluster, radio, a/c controls, steering wheel controls and dash mounted switches.
I had to remove one 7 mm headed screw from the trim panel above the instrument cluster. I also had to drop the lower dash trim panel to access two more 7 mm headed screws ath the bottom edges of the main dash panel. I tilted the column all the way down and placed the shifter handle down to D1.
With all of those steps completed the dash trim panel can now be pulled or unsnapped from the dash. The switches can be unplugged and the panel removed to access the interior screws for the headlight switch assembly.
Sorry, no pictures of actually removing the screws and installing the new switch but, I did get some pictures of the switch to let you have an idea of how it is mounted.
Further testing of the wiring to the switch should be done before replacing the switch.
Terminal “B”, orange wire should have power at all times. Power is supplied via the PARK LP fuse in the underhood fuse box.
Terminal “K”, dark green wire should have power with the park and/or headlights switched on. The panel dimming switch also needs to be rotated to the full bright position. This wire supplies power to the ILLUM fuse in the driver’s interior fuse box. If power is present when the above conditions are met, the switch is not the problem. If power is not present on the green wire after the above conditions are met, disconnect the harness from the headlight switch. Using a fused jumper wire with a 10 amp fuse , connect the orange wire at terminal “B” to the dark green wire at terminal “K”. The dash lights should now be on at full brightness.
The back side of the switch showing the electrical connection.
Now we have power to the ILLUM fuse in the interior fuse box.