Definately want the aircon - aircon dries to air meaning its able to pick up the moisture in the air of the car more efficiently.
That's why using aircon to de-mist your screen works so well.
Using the re-circ mode draws this moisture back into the system, dries the air out and then sends it back in the car to start again.
The only problem you may have is that the PD130 is so efficient that it doesn't produce enough heat to run the heaters at full when the engine's at idle - you might have to go for a very uncomfortable drive!
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