I have a 1986 f150 and recently i took apart the dash to replace my speedometer cable. While i was in there i decided to try and figure out why my instrument panel lights dont work. The top light bar works (where the 4x4, turn signal, and fasten seat belt lights are) but the lights that illuminate my speedometer, rpm gauge, and other gauges dont work. I checked all the bulbs visually and with a voltmeter and they checked out ok. I went on and tested the metal prongs of the wiring harness that plugs into the back of the cluster and i found that only 2 of the prongs were testing at 12 volts. The other prongs were somewhere around 0.05v. I dont know how many volts the light bulbs need to illuminate but it seems like 0.05v is way too low, so im assuming this is my problem. Any help as to how to fix this voltage problem (or anything else that might be causing my lights to not function) would be greatly appreciated.

 

If some of the lights illuminate when you turn on your parking lights and some don't then it is usually the printed circiut on the back of the cluster. There is only one feed for the cluster for illumination. Wire color LB/R illuminates cluster, radio, heater a/c controls, ash tray. Hope this helps