i installed a new head unit, and have had trouble getting my dimmer switch to work. right now dash lights are on full brightness and the dimmer switch does nothing. when i installed the new head unit i did not use a harness, instead i cut of the factory harness and rewired everything everything with the help of this post: http://www.xterraownersclub.com/ubb/ultimatebb.php?ubb=get_topic;f=38;t=001168#000001 the only problem is that the blue/red dimmer wire does not have a corresponding wire from the harness coming from the new head unit. if anyone could tell me what to do with the blue/red wire that would be great. hopefully that would get my dimmer working again.

Look at the instructions for the head unit. Usually the illumination wire is orange... I dont know that would fix your problem though.