It should just screw on like the low side on the accumulator

 

Are you using a 2002 operating system?

I have had to do that to get the fan controls to work right. They constantly stay on other wise.

 

Yea it's a 2002 os and pcm. You had to add the pressure sensor?

 

No it was a 99 truck. We had to use a 2002 operating system to get the E-fan control to work properly.

 

The pressure sensor needs to be there, for the pcm to see the need for the fan speed change.... Seeing 0 and having them cut on at 0 they will stay on constantly (on high)

 

First off, you have an 02 PCM, so hook up your fan triggers properly - to the PCM. You should already have FAN1 trigger ground on pin 42 (blue, I believe). FAN2 trigger ground should be RED pin 33. HP Tuner can configure the PCM for this.


Even without the pressure switch, I believe this still should work for you. OR, find a way to get that pressure switch included. Then, worry about adding your manual switch to ground pin 33.


I would not be trying to trigger using the AC circuit, easier using PCM, IMO.


Is this a viable solution for you?

 

I already have a manual switch that turns both fans on high that I have been using for the past couple of years. I like being able to turn on the fans at will, and when the truck is off. I also have the PCM controlling both low and high settings as it is now, so the switch is just a manual override.

I just bring this up now because I want the pcm to deal with the fans automatically since I just put AC back in the truck. It looks like the AC pressure sensor is about $30, then run some wires. Or my other option is of course just to do a relay like I have above.

 

Third time typing this...

Got this done today. Only hiccup I ran into was the AC clutch would enable with the relay connected to it between the PCM and factory relay. I didnt want the AC clutch to always be on with the truck off (Battery drain probably), but the weird thing is it would release if accessory or on power was running. I fixed it by putting the AC relay to 12v switched power instead of 12v constant (Battery like in my diagram above).

Everything works perfect now: PCM has independent control of low and high speed, high speed comes on with the AC clutch engagement, and my manual override button works correctly.

I decided I want to keep the AC pressure circuit open so I could use it as a 5v input if I wanted.

 

I haven't had any issues running oem fans and harness without the pressure sensor. Idling in 100 degree houston traffic with all the turbo heat. No issues. I keep ects in the 170s

 

Do you also have the high speed wired into the A/C clutch?