Dodge Repair: hvac, blower motor resistor, jumper wires

Question
2002ram 1500 5.9L 4x4 auto
heater a/c blower doesnt work have 11.75 volts
to blower wiring all the time no matter what position the fan switch is in incl. off
blower motor works fine with jumper wires off battery

Answer
It's good that you've got near battery voltage at the blower motor.  You've ruled out nearly have of the system.  Power feeds from the ignition switch to the blower motor.  If you jump the ground wire to chassis ground when the motor is plugged it you should have it come on.

Power goes through the motor and ultimately the ground is provided by the control head.  However, between the motor and the control head there's a blower motor resistor and depending on control head speed position will dictate which path through this resistor block the current flows.  Most of the time when one fails it defaults to high speed only and off.  All other speeds do not work.

I would suspect you have a bad blower motor resistor but the control head is still suspect.  The resistor is located near the blower motor itself.  It's cheaper and more readily available than the control had so I would start there.  

Let me know what you find and also get back with me if the resistor doesn't work.  I will try and walk you through another check to see if the control head is bad.
Doug