last winter i was putting in a 6 inch video screen and my buddy connect two grounds for the wiring harness together and they were suppose to be. It led to smoke coming up from from the guages and left me with no gauge lights and my air condition/temp/ screen lights would turn off if i have head lights on or jsut the guage lights. i took put the old head unit back in so it seemed like i never touched anything and took it to scion they replaced a fuse i didnt see and the guage lights worked (they also charged be 55$ and blamed it on my aftermarket alarm which is a hornet 2 way remote start) i also have the upgraded 100000 warrenty anyways well what has never been fixed and the lights for the center dash under the cd player the lights still dont work if the cars head lights are on or the cars dash guages are on. if i put the car in defrost mode that light still comes one but besides that i have all darkness for eveything below the cd player accept for maybe the seatbelt and airbag indicators. i ahve been driving it like this for too long and its anooying does anyone have any ideas i figured i would ask you guys before i go paying someone to fix it sorry for the long post thanks for the help.

 

There is a common issue with the 07's that sounds just like this. And causing a short or other issue with that circuit could potentially trigger it.

Just so happens I got one like that in to attempt to fix it and repair an led swap this weekend. Search 2007 HVAC Issue and you should find my post. I found the cause of his (poor factory solder joint) and fixed it. So there is a good chance it may fix yours. Let me know if you arent comfortable taking it apart and messing with it and would like someone else to look at it.