Wilde Racing

iTrader: (26)

I still don't understand why you guys with the newer (03-and up) PCMs, are using the a/c clutch to control the relay. Doing so causes a HUGE power draw when the A/C clutch and the fans turn on at the same time.........
Why not use the other PCM pin (36 I believe) to ground the relay and let the PCM have complete control over the fans like the 05 trucks do?
The computer will still engauge the fans for the a/c but only when the high side of the a/c system reaches a preset psi..
The A/C will work better, the fans will last longer (along with all other electrical componets imo) Less chance of overheating, better fuel milage, and less chance of blowing a fuse or relay.

ReSpAwN DeMoN

hey man I'm gonna try that out.

and last I heard the pin connections in the PCM are not high drawing lines so I can shove the wire in there...

I'll get back to you on this..

Wilde Racing

iTrader: (26)

Don't just shove it in there The PCM can only supply a ground for a small load, Like a relay!

ReSpAwN DeMoN

so what do you suggest I do?

The harness I got is from DLH2006. Good harness..

I connected the ground wire to the alternator bracket.
The power wire to the power bolt in the fuse box.
The PCM wire to pin 42
Now I got this green AC wire diong nothing right now.

ShakeNBake

I think what he is saying instead of using the dark green wire for the ac which is what i used to get a pcm pin and take the ac wire from the harness that you bought and run in to pin 33 on the pcm that way the pcm is the only thing controlling the fans, after tuning. If this would work i would be interested in doing the same so let me here if we are able to do this or not. It makes sense and sounds reasonable to just pcm pin the wire from the purchased harness and use it and its relay.

ReSpAwN DeMoN

When it comes to electricity I'm an idiot.. so let me get this straight. I PCM pin that ac wire on my harness and put it in pin 33?

yet.. wildracing said do not do that.

ShakeNBake

the ac wire is wired to a relay on the harness he is saying dont just hot wire a wire to pin 33 you need a relay. but the ac wire is kicked on by a relay.

Wilde Racing

iTrader: (26)

O.K a quick lesson in relays for those who need it......


Basically a relay is a remote switch

You have a small housing with four wires.
One wire is HOT all the time or when the key in on this is the "Supply"
One wire is hooked to what ever you want turned on (fans) "Delivery"
The next two wires "Switch control if you will" are used to energize the coil and make the "Source" poll contact the "Delivery" poll. One positive and one negative.
Sense the only work being done by the "switch circuit" is to make the "Supply" Contact the "Delivery" it draws a very low amount of currant.
The positive wire for the Relay "switch" is what wire you tie into the a/c system with, but if you want to let the PCM control the fans, you need to supply pos. voltage to the "A/C" (green) wire and connect the ground to the PCM.....Get it....
I'll post a diagram in a few, with detailed instructions.....

ShakeNBake

thankyou that makes sense now

ReSpAwN DeMoN

yes thanks, that did clear thing sup a bit. I would also appreciate the diagragm thank you..


so! the pcm wire.. is connected to a relay and pin 42..

the ac wire is connected to a relay.. put a .064 micro terminal on the end and push that through pin 33 (36?) and it should work fine?

ALSO.. would there be a problem with hooking the fans up to a constant 12vdc and have them on full blast when vehicle is on.. and have them both off when vehicle is off? is there a way to rig that up?




and one last thing! I notice sometimes when the ac fan fails to come on the compressor will constantly try to turn on even though its already on and I can feel it engine rpm's drop and the engine revs up to compensate and I really notice it take away from power. I almost feel bad for it. Can this damage my ac system or any electric system when it keeps trying to do this?