I am posting this as a solution because I was not able to find any good information when I was searching for a solution. My AC/heat blower was working on every setting except for high and the rear blower was not working at all. The problem had nothing to with the resistor as the resistor only provides power at the lower settings. When on high there is a completely seperate circuit that feeds a full 12 volts to the blower. This same circuit provides power to the rear bolwer for all fan speeds. There is a fuse in the underhood fuseblock (i believe 30A) that protects this circuit. In my truck someone had removed this fuse and used it to the position for the brake lights where there should have been i believe a 50A fuse. As soon as I put a fuse in the empty location everything worked perfect. I hope this helps someone. Like I said I could not find any good information on how the system worked as far as where the power feeds are coming from and what speeds are controlled by the blower motor resistor. It wasn't until I studied the wire diagrams for a while that I realised there was a seperate cercuit for the high fan setting.