Starting a thread on this topic. While it isn't anything we truly need, I think this would be a neat little mod. Looking at the wiring diagrams it'll only require sending a 12v hot to the control module and adding a relay off power from the ignition switch. I don't have all the wiring worked out yet completely, but as I get it all sorted this weekend I'll update.
This is one of those little mods I like doing that has little purpose other than novelty, I never really use the folding mirrors and don't parallel park very often. But I'm bored and need something to do haha.
Using these wiring diagrams:
http://www.mitchell-auto.ru/UserFile...audi-s8-wd.pdf
We find that on page 37, FIG. 36 that the module is powered by a blue wire on PIN 4. That must be switched power from the ignition switch. Powering that off the time delay power or with a constant feed should allow us to have folding mirrors with the car otherwise off (much like how the radio will work for a period with the key removed yet the windows will not).
The switch on the door does nothing more than provide a ground that energizes the module. So then all we need is a relay that will create ground with the key off, and that will open when the key is on. Simple enough. For this I'll be using the original keyed 12v that was energizing the module. I'll have both the new relay and the original mirror switch wiring run to PIN 12, thus the switch will still work as well. With the car on it will open the relay and won't ground, key off it'll give us the ground and mirrors will fold. I'll provide pics and further info (and video) when I complete the work.
The final design went something like this: power to PIN 4 is cut and a constant feed is brought in from the relay box (Several all-time hot 12v locations at the base of the fusebox, just grab power from there). Off the keyed power we add a double pole single throw relay, when power is on via the key the relay powers a pin that is open, and when off the other pole flows to ground and from that ground to PIN 12. At PIN 12 we splice this wire in with the other wire that feeds there. I'll draw a diagram shortly to better illustrate this all.