more on possible causes for aux fan to run high all the time when AC is ON.

"...the electric cooling fan is controlled by the ECM via the output final stage. The output final stage is mounted on the fan housing, next to the fan motor. The fan is operated using a pulse width modulated signal. Fan circuit wiring is protected by a 50 amp fuse. Electric fan activation is based on the following inputs to the ECM:

• Radiator outlet temperature
  
• Calculated catalytic converter temperature
• Vehicle Speed
• Battery voltage
• Calculated A/C pressure
  

When the vehicle is first started, the ECM activates the fan briefly at 20% of its maximum speed, then switched off. This is for diagnostic monitoring. The voltage generated by the fan when it slows down (acting as a generator) must match the stored rpm values in the fan output stage to confirm that the fan is operating correctly.

There is a control module mounted to the aux fan housing that receives a variable signal from the DME, which then controls fan speed. It may be bad. The PWM speed control is inside the fan motor housing, it's speed is continuously variable from the duty cycle of pulses it receives from the DME.

So its either the PWM on the Fan housing is bad or DME is sending signal to PWM to run high seeing AC pressure is High.

AC has 2 pressure input Low and high, low is used to put the gas. I also see a sensor on the high side (small pipe).