Here is a voltage reducer that should work for your fan motor.
[on edit] After reading JonG's post below, this one is probably not stout enough for a fan motor. Rated at only 4 amps. Might work with a 6V motor drawing 4 amps, but who knows what your 12V fan motor is drawing. if you use it, it may let the smoke out.

Last edited by klhansen; 11/01/2025 11:32 PM.
Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.