Which "hot" - the coil feed or the power feed? Tracing backwards from the fan motor (in my 1990 FSM - other RENIX years similar...)
Radiator Fan Motor - the black wire is the ground, and is secured to the driver's side fenderwell. The Red wire is power, and comes from the cooling fan relay contacts.
Cooling Fan Relay - The OTHER red wire (the one that doesn't go to the cooling fan motor) goes to splice 10/8, which is an 18AWG green wire coming off of the start relay binding post. CAUTION - there are several green wires - you want one of the ones that has a 20AWG orange companion. That narrows it down to two - the other goes to the ignition switch.
I do not have a listing for splice 10/8, but backtracing the wire should locate it for you.
The distribution is handled via fusible link wire - if the link is blown, the B+ Latch relay won't work either (which will kill a few other functions, but I don't recall which offhand.)
5-90