E38 AC Pressure Switch Control

[JohnPShoe]

I am trying to allow the E38 to turn on the cooling fans when the AC pressure reaches a certain psi. The vehicle is a conversion and the OS is a 2011 Silverado 6.2. The tables are present in the System:Fans portion of the tune, but I am not having any luck having a scantool see the valid signal in the ECM. Is there a possibility that the OS is inhibiting this function? The wiring diagram shows pin 12 is the pressure signal, pin 13 is the lo reference, and pin 34 is the 5V reference. I am lost as to why this will not work. I have attached the tune for anyone to look at. Any help is appreciated. Thanks!

19349

[DURAtotheMAX]

Its because you dont have a factory HVAC module there to send an AC request/info via GMLAN.......

[JohnPShoe]

Its because you dont have a factory HVAC module there to send an AC request/info via GMLAN.......

I am using the BCM, but not the HVAC module. I know the E67 guys have made it work without the HVAC and BCM. I am hopeful there is a solution for the E38.

[VEGASROBBI]

I do have a BCM on the net, I am controlling the AC clutch off evaporator feedback. I have used E38's to control the fans off condenser pressure many times before without the HVAC controller or BCM. Unlike the AC request signal sent from the HVAC module to the BCM then to the network the AC pressure signal is hard wired directly into the ECM.