I have a 2006 F-150 XLT 5.4; the lights on my instrument cluster lights do not work; also no lights on heater controls. Gauges (tach, fuel, etc) are all working properly. Replaced bulbs, checked fuses. Please help, cannot stand not having dash lights.

 

Bad rheostat (dimmer switch)?

 

Thanks, I will try this. Is there a way to test the rheostat?