Join Date: Mar 2002
Location: Austin, TX, USA
Re: Electric Fan Power Source
I agree with Dale. While you could use the horn relay, the 8 ga wire to the horn relay is supplying all power to the vehicle. When you add the 30 amps or so drawn by the fans, you're likely to see some voltage droop and some heating of the wire between the battery and the horn relay.
Your wiring looks very nice. If you still have the junction block behind the battery on the radiator support, tap in there with an eyelet terminal and a piece of fusable link. Install a self reseting circuit breaker in the same general area and use that power supply to feed the fan relay. That'll keep your main power feed isolated from the high current of the fans and be plenty safe.
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI