Did you check to see if it runs with the fan speed set to High, or Max, whatever the top speed is?
When you said your motor is good, I take it you hot wired it and it ran. That's High. To run slower, the switch routes the power through a resistor pack that lowers the speed by dropping the voltage to the motor. If that burns out, it gets no power till you select High.
You see the connector side (left side in this photo). It's mounted on the HVAC air plenum somewhere, so the resistor side (right side in photo) will be inside where it's cooled by air flow. The pic may not be for E-Series, it's just one I found online, but the idea's the same.
EDIT: Actually, my lookup says it DOES fit, if you chassis is 1999. And probably many other years, since I first found it as 2005. At least find the resistor pack. The connector might be loose or damaged.
Look on the ducting, maybe behind the battery, but near the blower motor, passenger side. (Suggestions from WEB, I don't have the RV nearby or a manual to look in.) Knowing what the pack looks like should help you spot it.
