Im trying to wire my efan with a relay. I need a trigger wire that will turn the fan on when I turn the key on. The second fan is on a switch inside the cab. Thinking about something in the fuse box but not sure which one would work.

 

You need a wiring diagram for your truck. But it is very easy just to check for key hot sources.

 

I tapped a 10A ECM fuse in the fusebox.

 

Under the fuse box, pick any pink wire.

 

Why do you wanna do that?

Just probe the empty fuse slots in your fuse box under the hood, there should be atleast 2 that are hot with the key.

 

Because its easy, and looks cleaner.

 

woops.. meant why is he triggering it when the key is on vs with the PCM.

 

this^ there is a set of four empty slots, IIRC, two are always hot and two are keyed use a test light fast and easy

 

I got to thinking, I know its never good lol
If I take the trigger wire on the relay to the battery and the ground to the pcm pin 42 on the blue connector, like it is on the org. nelson harness, and set it to come on at the desired temp, would that work? The pcm is already pinned, just have to connect the ground wire.

 

nevermind. I got it working