2001 LS - This one has me stumped. At night, the dash lights go completely dark and the Nav screen lights up full bright as if daylight mode (at night / dark). I've tried adjusting the dimmer switch (wish it was that easy). It's also not the "Night mode" option on the Nav screen. This has happened intermittently over the past several months, working just fine for months then last night again dash lights out and Nav screen on bright in daylight mode. Is it possible that the dimmer switch itself has gone bad? Is it the ambient light sensor? How can I test?

Thank You in advance for your thoughts.

 

This is just a remote possibility but doesn't hurt checking.
Intermittent problem points to electrical connection not making it all the time.
Your fuselink might be "slightly" blown. Look for the 140A fuselink. These are bolted so there is some work to closely observer them but you can see them from top as well without removing anything. It is just hard to see through the colored cover.

 

Thank you, I'll take a look at that fuse. I agree that it may be some short / connection issue - which makes finding it a real pain.

 

How long ago was the battery changed? Many electrical glitches in our cars are due to dying battery.

 

The battery is only a year old and still cranks strong. I know what you mean though, a shorted battery will cause strange issues like the one I'm still experiencing.

 

This screams "blown parking light fuse" to me. See if your parking lights still work. If not, you found it!

Though, on second thought, if it was intermittent in the past the next culprit would indeed be the dimmer switch.

 

Was this ever solved? If yes then what was the problem?