Had the same problem with my 2000 1500 van. Just replaced the resistor (Plug in unit under the hood on the A/C shroud on the passenger side held in by 2 screws) and problem solved.
If it has only high speed, the blower motor resistor has to be replaced to get all speeds back.
The blower motor resistor pack is bad.
The resistor block or blower motor resistor is used to control the speed of the blower motor. That is how you get the lower speeds on your air conditioning or heater. The higher the resistance the lower the speed of the motor.
The heater motor speed resister is burned out.
Heater motor speed resisters are usually located close or nearby the heater motor.
blower motor resistor is burned out
Blown fuse, defective blower motor, defective wiring, defective blower motor resistor pack, or in rare instances a defective blower motor speed control.
Probably the blower motor resistor is fried. New ones from Dodge dealer are usually about $20 for the part. A very cheap and easy DIY fix.
double check that it's the motor most times it's the resister for the fan speed In the firewall on the passenger side of the truck is the blower motor speed resister coils, they burn out alot. I could not find one for my Dakota so I got one from a dodge caravan and I changed the wirring, that is the most likely problem
In general the heater blower motor speed resistor is located in close proximity to the blower motor.
Blown fuse, bad fan speed control switch, bad blower motor resistor pack, bad blower motor, or loose or disconnected wiring.
You'll find the heater blower motor resistor in the heater/air conditioner compartment. This compartment is location underneath the dashboard. This is the part that allows the heater blower motor to change the fan's speed.