The dash lights have quit working on my 87 F150. ALL the other lights work EXCEPT the dash lights. I've checked all fuses and they are all good. I've taken the instrument cluster and head light switch out and traced out the wiring. I feel comfortable saying that the head light switch is good. The potentiometer is good and the wire leaving it is colored blue w/red stripe. I've checked the bulbs on the instrument cluster and they look good with only a visual look. I've done voltage checks and continuity checks on the blue/red wire. However I can't find the other end of it. The Chilton manual doesn't show the potentiometer at all. I know the tan/white wire feeds the switch and that wire does have voltage on it. Pulling the switch then feeds the brown wire which is one side of the potentiometer. The other side is the blue/red wire. From what I see it should be the wire feeding the dash lights. Does anyone have a diagram of this wiring or know what wire does feed the dash lights?

 

Brown is variable power out to the instrument lights. (all the dash lights are on this rheostat/potentiometer)

If you have tail lights the fuse is ok.
If you don't, check the fuse at the top center of the box for continuity and probe that socket in the fuse box for power. (the connector could have come loose on the back side)

The plug connector to the headlight switch is known to overheat and melt causing shorts and open circuits.
A replacement plug with pigtails is commonly available in the aftermarket.


If it's just the cluster and not every light in the cab (ashtray, wiper/light switch's) then I would take a magnifying glass and check the foil traces on the Mylar harness behind the cluster.
Sometimes the copper foil flexes and breaks or the connections just get corroded.
Clean up any oxidation with an ink eraser or Scotchbrite pad.

Hope this helps.