Pontiac Repair: High Speed Fan Swith, pontiac firebird, motor circuits

Question
ON 1989 Pontiac Firebird with 2.8 engine,fan switch will only turn on blower motor in two lower speeds-high speed fan switch position results in blower motor not running at all? I have replaced fan switch in console, high speed blower relay out on passengers side of the engine compartment as well as the resistor assembly that is located next to the blower motor. I'm think that the fan motor circuits are separate from the A/C electrical circuits?  Thanks  Bill

Answer
Hey Bill:

this is a trip down memory lane... Yes the fan is seperate from the a/c system. You may have a blown fuse or a power supply issue to the his speed blower relay. The relay runs high speed on the fan. If your are missing a power feed to that relay then that is the problem. Turn the key to run and turn the fan speed on high there should be 2 seperate power feeds into that relay if not then you have to trace the high spped input to the relay back or the battery feed to the relay back to find out what you are missing in this equasion. You may also be missing the ground to the relay also. Good luck :)