just a follow-up
The resistor was bad....burnt to a crisp. After some minor repairs to the plug and installing the new resistor pack, my fan blower motor works on all speeds again.
For reference, the resistor pack on a 96 f-250 7.3l turbo diesel is NOT under the dash. It is actually in the engine compartment, up near the firewall directly under the AC condensor. After removing the washer fluid container and moving the heater hoses out of the way, I was able to reach it for removal and replacement.
Thanks again for your help.
Camconative