I finished up an electric fan conversion except for one part; tappin in to a 12V switched power source (turns on and off with the ignition switch). Is there a wire in the underhood harness (definitely NOT the coil wire, I know that's taboo) that I can tap into or would it be best to run to the fuse panel under the dash? I already have a relay, circuit breaker, and fuse mounted out under the hood.

 

Click my signature link & look in the Fuse Terminals album. If you're using a relay to control the fan, you can tap power for the switch that controls the relay to just about any stock circuit, depending on how you want the fan to behave. If the switch will control the fan DIRECTLY, then it needs to have a dedicated fuse near the battery.

 

I already have a 30amp relay and a 30amp circuit breaker (both located close to the battery) in the fan circuit. The fan wiring kit is like this:

http://www.jegs.com/webapp/wcs/store...58607_-1_11471

My concern is tapping into a 12V switch source under the hood and it causing other issues like a lack of voltage to a sensor, etc. If I'm understanding what you are saying then it would be okay to tap into the 12V switch power for the coil?

 

That link doesn't show the circuit diagram.

If you're putting the switch on the dash, tap a dash circuit. That way, you're not running 2 wires thru the firewall. Get a Haynes manual & use the diagrams in the back to figure out which circuit you want the switch to run from.

 

Ok....Going to describe this diagram to the best I can. It is similar to this but without the toggle switch.




I only have one wire to run and that is to the switch power. I found an open circuit that is unused in my fuse panel (for power windows, don't have them on the truck). It comes on when the key is in the run position and this is what I am needing. I'm just going to drill a tiny hole in the firewall, grommet and sheath the wire, and run it to this power source.

 

I have a lot of respect for Ryan, and he knows his $#!+ about wiring, but that diode just isn't needed. All it would do is make the fan stop faster when the relay turns off, but it would put more stress on the brushes & motor windings; and on a vehicle with good airflow thru the radiator, you could even burn up the diode.

 

Exactly. I'm not using a diode on my system in order to let it free-wheel when it turns off. I finally got the wire ran into the cab and drove it to work tonight as a test run ( with a butt-load of jumper wires and relays just in case and it worked perfect.