Sigbert,
What "drive" did you have replaced?
The 1984-1994 Service Manual schematics show a booster fan that is electrically controlled, but I don't think this is the engine cooling fan. Diagram is on page E-0028. Access Coach Assist, then Beaver Motorhome History, then Schematics. The Service Data section shows a diagram for the engine compartment cooling fans, again electrically driven, but not the engine cooling fan.
Based on the above, I'd guess your engine fan is hydraulically driven and controlled by a wax valve.
Steve