I haven't looked at how the coils are laid out, but as long as the ac coil is before the heating coil, it will cool the incoming air in from outside, causing the moisture to drop out of the air, then the heater coil will warm the air back up again. That's how 'air conditioning' works, you adjust the moisture by cooling as required then reheat it. Which is why you have the ac on when you are demisting the windscreen, warm air will com out, but it will have had a lot of the moisture removed first helping it clear existing moisture.
A forum community dedicated to Volkswagen Mark 4 owners and enthusiasts in the UK. Come join the discussion about performance, modifications, classifieds, troubleshooting, maintenance, and more for the Golf, Bora, Jetta, Touran, and Scirocco!