Your climate control has an ECONomy mode button. I believe on an E420 it is located just below the display and says "EC". It should light up a red LED when you press it, to let you know the system is in economy mode.

The system runs exactly the same as in Auto mode, but the A/C compressor never kicks in. Watch for fogging up windows and if they occur, put the system back into Auto mode for a few minutes. I tend to do this in really rainy weather, as the windows fog up too fast in Economy if it is humid out.

Neal

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