All I can add is that my 3L Roadster had the air conditioning radiator slightly slanted underslung between the chassis rails and did not require the (switched) fans on whilst moving, there was more than enough passage of air thru the radiator for the air conditioning radiator to work without the assistance of fans. Only when in very slow moving or stationary traffic did I need to switch the air conditioning radiator fans on.
I also had a Sifab ali radiator fitted with standard thermostat ,and the airflow thru that may have been affected by the lower slung air conditioning radiator, the ali rad. ran only slightly cooler than the original radiator, with the fan only coming on in slow moving or stationary traffic for both the original and ali. radiators. Which was reassuring as I had read that the ali rads were much more efficient and do run the engine much cooler than the engine was designed to operate at
