Variable speed switch works with "3 speeds motors", not 2 speeds motors. 2 speeds motors only works with 2 speeds switch.

I actually can't recall if 71s got 3 switches options ( 2, 3 and var speeds ) or 2 ( 2 and var speeds ). Is a fact since 72 just 2 and 3 speeds were optioned, not anymore variable.

Have to search on the 71 parts catalog.

Sometimes the 3 and var speeds are mixed up since both work with the 3 speeds motor.

My 74 parts catalog labels the 3 speeds switch like 3/var, but is not var, just 3 speeds. Dunno on 71. Will find out tomorrow.