I have an 06 mustang Roush that when at night I go to adjust **** to brighten dash lights they wont brighten at all, but they are on, but very dim! I'm guessing adjustment **** is bad but before I buy any thing else it could be? Thanks Paul

 

Paul, as gravy said it could be any of those. But, I would start with the easiest first. Check the sensor to make sure it's not dirty, then move on to the switch itself. Good luck.

 

Even if you disconnect , then reconnect battery ? Maybe someone had that part of dash out & could be something's not plugged in right, lord knows I've done that replacing stereos with my heater controls. You know passenger side kick board fuse panel has a 10 amp fuse that operates that area try that fuse first if you haven't yet. Could be to some don't get the cabin polin air filters in right or under that grill where you access the polin filter the rubber guard on the side gets loose and allows water to run down , thus maybe causing a short as well.

 

Top red 10 amp fuse to the right