Dash Dimmer Switch Solution

Some of you may know that the dash light in B series trucks are known to fail. Many have had problems with the dash lights not working. I have found that usually the problem comes from the dimmer switch in the dash.

To test to see if your dimmer switch is bad all you have to do is short terminals B and C on the dimmer switch socket.
To get to the socket you will first have to remove the 4 screws holding in the speedometer cover.
Once you have the cover removed just unplug the socket from the back of the dimmer switch. If you’re looking at the socket as shown below, just take a wire and short out the two terminals in the socket that are facing the same direction, terminals B and C, and turn on your headlights.
If your dash lights light up your dimmer switch is bad, if not there is a problem somewhere else in your dash electrical system.
Warning: Do not let either terminal B or C short with terminal A this will blow the fuse.

Note: The dash lights are hard to see during the day and I suggest performing the test at night or in a dark garage. Wire shorting terminals B and C shown in blue.

As long as C and B are shorted going into the plug your dash lights will show at full brightness.
So you have multiple ways you can short out the two pins. If your happy with just keeping the switch unplugged just make a jumper out of two spade connectors and put some heat shrink over them, then insert the jumper wire into the plug like shown above and you’re done.
I didn’t like the idea of the plug flopping around in there with wires hanging out of it so what I did is disassembled the switch and soldered a piece of 5A Fuse across where the two pins solder to the switch board. (The arrow Below)

To open the casing, you must take a small flat head screw driver and get under the top of the case and pry out. It’s a little tricky the first time you do it.

Being since the switch is essentially useless now the simpler way is just to leave it unplugged and run a jumper from pins B to C in the socket and leave the switch in the dash just for looks.