you need to use a multi-meter to determine if you are getting any current to the fan, most likely not, based on what you have described. you will need to trace the wiring back to the source and ascertain if the circuit is good or not.. if you don't have it would be a good idea to get Niger Calder book it describe what step you would want to take in alot more detail than I have done here.
best of luck..

With all due respect, Barry, before you even removed the old fan, you should have ensured that the circuit feeding the fans had 12+V. If yes, then you could carefully clip the wires to the non-working fan and verify that there is 12+V right there at the fan. [I say carefully because you will need room to butt splice to reconnect the wiring.] If you have voltage there, then it is a fan problem. If you don't have 12+V at the fan wiring, you know you have a circuit problem and (probably) not a fan problem.

Barry, Catalina did not install fans, so it must have been done by a previous owner. No way of telling if there is a fuse or not. Which circuit does it run from? Lights?

This is not rocket science to troubleshoot. You say you have it connected, so just check voltage at the positive and negative lead to see if it is getting power. If you don't have a cheap voltage meter then run down to Radio Shack and get one. My guess is that there is no power to the fan, but you have to check. If there is no voltage there, you will have to trace the wire back to see where it comes from and check for voltage there.

Alternatively, if the old fan is available and the remaining wires are long enough, touch them to the respective battery terminals. If it spins, the fan was not the problem.

Good idea. I always carry a pair of 'jumpers' in the form of 18 inches of #12AWG wire with an alligator clip on each end. That would make it work even with the fan wires too short.