Trucks blower moter will not work on 123 setting. Works on 4&5. Whats up anyone? Where do i start?

Blower motor resistor...passenger side footwell you should see a connector coming out of the heater core assmebly. Its about $25 at the dealer and ten minutes to change.

http://www.dieselplace.com/forum/showthread.php?t=231606&highlight=blower+resistor be sure to follow the link in post #3

and more reading
http://www.dieselplace.com/forum/showthread.php?t=240401&highlight=blower+resistor
http://www.dieselplace.com/forum/showthread.php?t=237990&highlight=blower+resistor

Thanks guys. Doesnt seem to bad,I ll check it out!