Reply to thread

Message: <blockquote data-quote="ttocs" data-source="post: 1150882" data-attributes="member: 11896">after a quick search for "99 mustang defroster schematic"one of the topics that came up from a different forum and explains it a littleyour problem is in the 99 mustang they used a smart rear window defrost switch that did not feed into the instrument cluster. in the 2003 they used a basic switch to "tell" the instrument cluster module to activate the rear window defrost relay. in the 2003 the only thing that is the same is the ilum. all the other wiring and what part controls the system is different I assume you are using the 99 cluster in your car? it will be way to complicated if not impossible to make the 2003 cluster work in your car. and it will be kind of complex to make the 2003 switch work with the 99. you might have to make the 2003 switch activate the 99 switch that will be hidden in the console area. and you can't just "tap" into the same colored wires on the 99 harness. even if it went to the right pin in the cluster, the 99 cluster will not have the logic built in to control the rear window defroster.  if i was you i would hide the 99 switch inside the console and use the 99 switch. leave the 2003 switch wired to light up and not do anything.</blockquote>