This 1995 Chevrolet S10 came in with the complaint that the dash illumination lights do not work. The customer drives a good bit at night and does not want to take a chance on getting a speeding ticket. A quick checked showed that the tail and license plate lights came on, so I knew that the park/tail light part of the circuit was okay. This is important to know. Dash lights are designed to not work whenever the tail lights are not working. This is a warning feature to allow the driver to know that the tail lights may not be working and they should be checked.
I checked the illumination fuse located in the fuse #4 position and no power was present. If power had been present and the fuse was good, I would have one of two problems. Either all of the bulbs would have been blown or the common ground would be faulty. No power at the fuse meant that more than likely the panel dimming switch was faulty.
Someone had been in this dash and the trim panel was very loose. I removed the two upper screws.
I found that it was loose enough to pull the corner out far enough to access the headlight and panel dimming switches.
I unplugged the panel dimming switch and checked for power on the brown wire with the tail lights switched on.
Power was present on the brown wire.
I used a fused jumper wire and connected the brown and green wires as shown below.
All of the dash lights worked.
Diagnosis and replacement of a faulty panel dimming switch.
The switch uses two locking tabs to hold the switch in place. You have to lift them a way from the switch to release the locks. The locking tabs on the switches can be seen in the picture above. They are in the middle facing each other.