Vintage AC and kicking on fans

[Richard]

Originally Posted by 6600DURAMAX

My tuner says that this ECM doesnt have a AC pin it was controlled by the BCM

This is true for the e67 ecu I am using. My understanding after much research is the fan control is separate from A/C control. Therefore if the pressure sensor is installed and the ecu sees the high pressure it will send appropriate fan signal to the fan1 wire (on/off or PWM signal). Ecu does not need an A/C command. Your tuner said it "A/C is controlled by the BCM"
Edit- Popped into my head. Maybe look at the pressure sensor signal to ecu as "A/C is on so turn on fan" I am using this to integrate the pressure sensor and high/low pressure switch. https://bp-automotive.com/product/ls...re-transducer/ The pigtails for the switches are available but not sold by BP. What ECU are you using? The great benefit of using this option over the A/C compressor lead is that the fan will only run when needed. Using the compressor lead or cycling switch will make fans run always when A/C is on. Fan is not needed at highway speed. Eliminates trinary switch and extra wiring.