Manually Powering a Relay?
 

Hey guys got a quick question on electronics.


i've been toying with an idea to just the wires to my electric fan and hardwire it to a switch in the cab.

i just had a second though. The fan is controlled by a relay correct? Is there any way i could manually power the relay. Say run the wire from the switch to the relay, and that way i could turn it on when i wanted and the computer could turn it on if it wanted?

Yes. However be sure you put a diode on the wire going to the PCM so it doesn't power the wire and hurt the PCM.

diode? Would it be easier just to wire in the fan to a switch and completely pass the pcm?

Not really. It is just 1 more component. The diode is only to allow the PCM to switch on the relay if it wants to and prevent voltage from entering the wire when the hard wired switch is on.

How would i go about finding the power wire? Relays do nothing but confuse me

Did some checking...

https://www.cherokeeforum.com/f2/pow...y-issue-93189/

If the PCM grounds the relay pin you shouldn't need a diode.

so according to that thread, i should run a wire from 1-4 with the switch inbetween and id be good to go?

no according to 98fourdoor's post it would be ground connected to one side of the switch and the other side gets wired on pin 2.

Ohh ok so i would be manually opening the ground instead of waiting for the pcm to ok it. gotcha. what gauge wire should i use? and do i need a fuse?

Regular stranded 20 gauge automotive wire will suffice. A relay doesn't draw much power. For the fuse... since you are supplying ground if the wire gets chaffed the worst that will happen is the wire becomes grounded and the fan won't turn off.

Awesome. Appreciate the help.

Good luck, wiring is always fun :)

Electrical is my major downfall so I always look for help when it comes to these things. It's not bad once you understand it

Ok, ran into some issues.

Everytime I hook it up the fuse #10 inside the cab kick panel blows. Ideas?

the post that takes about the fan is on a 88, i dont know the year of yours. but looking at it, the number 2 pin gets plus from either the temp. switch or the ac relea.
this is why you blow the fuse,
so you would need the give it a plus. i would connect my switch to plus in one end, with a fuse, and the other end the the wire from the temp switch, which not has not has plus with ignitionkey in position on. that way you dont need a diode. if you connect directly to the relea, you will need a diode.