dimmer switch wont dim?

[03EXPO4x4]

I have a 2003 expedition and my digital readings on the dash are very dim almost unreadable. Radio and climate control is readable. Dimmer switch will turn on and off dome lights but have no control on my interior radio/climite/dash lights. I have already replaced the switch and it is still doing the same thing. what do i try next?

 

[stamp11127]

I'm looking at the diagrams for the 2003 Expy. They don't show a dimmer for the Expy but they do for the Navigator.
Where is the dimmer switch located - separate or with the main light switch ? I'm hoping it isn't with the main light switch. If it is, how are you at following wiring diagrams with a meter?

 

[Hamfisted]

It's a rheostat dial (up/down) in the main light switch. If for some reason it doesn't work you'd have to replace the whole light switch. Since you've already replaced the switch once with no improvement you'll probably have to start probing around with a multi meter checking voltage and grounds. The Expy doesn't by chance have an aftermarket stereo in it does it? I'm just wondering if a previous owner dorked with the illumination wiring behind the dash. But a new Motorcraft switch is about $65 from Rock Auto ( 4L1Z11654CAA ).


-Mike


The dimmer switch is the up/down dial to the right of the knob on the light switch....

 

[stamp11127]

It may look like a rheostat but it sends out a pwm (pulse width modulated) signal according to the diagram. So there are electronics in the soup that determine the lamp brightness.

To the op, do you have a meter and are able to read wiring diagrams?