On the variable switch, there will be one prong left empty (pretty sure it's the B/U prong on the edge that is a ground), but some wiring has to be changed at the switch. There are little letters molded into the back of the switches. You might need a magnifying glass to see them. If you refer to the wiring diagram, you'll see that...
the red wire that went to "A" on the 2-speed goes to F-1 on the variable switch.
the brown* (w/ stripe) wire that went to F-1 on the 2-speed goes to "A" on the variable switch.