Hey guys. I'm going to be using twin derale 2 speed fans on my car (PN 16925.) I want the PCM to turn the fans on and off. I have a standalone harness and it has the 2 outputs pre-wired for fan control. I am also not going to have AC on the car. How would I wire it best to control both fans?

I have seen some people use a 3 relay setup but I thought that was for a car with AC? I just want a simple setup, but if I can get both a low and high speed setting to work, since the fans I'm using have that capability, then I'll go that route. Just not 100% sure how the PCM originally controlled the fans on a stock 4th gen.

 

 

So which one of the diagrams would you recommend I use? I'm assuming the first one? Will that just kick both fans on at once and only at one speed?

 

Well..... i would guess if you got TWO outputs for fans on your harness I would place a pretty good wager the diagram you need is behind window number 2.

 

do you have two fan turn on temps loaded into your computers tuning? Or need the a/c function to turn on a fan as well? Then it would be the first pic. Otherwise just run the first fan turn on to both relays to turn on both fans if stock tuning and no a/c

 

Is this what you wanted?


I just used two relays. works fine and is all you really need. and yes one speed.

below is how you get two speeds

 

Looks like I'll be wiring them the simple way then and having just one speed for both fans. Now I'm just wondering if I should have them both come on in low speed only, or high speed only? Probably high just to be safe even though I'm not sure if the car actually needs it to stay cool.

Anyways, thanks guys.

 

if you're going the 2 single speed fan route, use the pcm to turn them on like shown in Pocket's second diagram; it will have one turn on at a lower temp, 2nd on higher. should be more than adequate for most applications.

 

It looks like they'll both turn on at once according to pockets 2nd diagram since both relays are only tied into one of the PCM fan wires. I'd like to use both wires and turn them on seperatly like you mentioned at different temps, but I'm assuming I'd have to use one of the PCM wires for one relay, and the other PCM wire for the other relay for that type of operation. Unless I am reading the diagram wrong?? Either way, it seems like it's a simple thing to set up.

 

sorry, looks like i didn't read through it all the way. this is pocket's add-on fuse & relay setup that i went with, should give a better idea on how to wire up the relays to move each fan independently.

going with the fbody wiring diagram, B42 should be fan 1, R33 for fan 2