Other, less likely, possibilities include:
* Faulty blower motor switch: While less common than a resistor issue, a problem with the switch itself could prevent lower speeds from being selected.
* Wiring problems: A short or break in the wiring related to the lower speed circuits can also cause this symptom. This is less likely than a resistor issue, but possible.
* Blower motor failure (partially): A failing blower motor *could* cause this, but usually presents as intermittent operation or noise, rather than just high speed only.
In short: The blower motor resistor is the most probable culprit. It's relatively inexpensive and easy to replace, making it the first thing to check. You can usually find diagrams and instructions online specific to your year and model of Dodge 1500 van. If you're not comfortable working on your vehicle, take it to a mechanic.
