should be the connector in the ac housing closest to the blower motor
Short of it is the resistor controls the fan speeds for the blower. Easy to replace and to my knowledge only available through a dealer.
behind the glove box
No such part exists
This website might be helpful.www.dodgeparts.com/
The blower motor speed resistor is burned out.
It's close to the blower motor.
It is under the dash, behind the glove box.
Your truck has both. the resistor is between the switch & blower.thje resistor controls the blower speed
When you beat the blower motor, you are probably shaking the blower resister. The resister is what controls the blower speeds and is probably bad or loose.
You need to replace blower motor resistor.
I would suspect the blower motor speed resistor is bad.