Testing Parked Car Ventilation

1) the feature is not temperature dependent. It will work winter or summer.
2) the feature will not activate unless the ignition key is in position "1". I.e., the ignition must be off, but your ignition key must be turned on suffieiently to unlock the steering wheel.
3) in early E34s, in all early 750iLs, and in all later E32s, the OBC's "timer" function key has a dual function, which was activated by "toggling" the timer button to the left or to the right. Toggling to the left activated an elapsed time function, but is not in effect on E34s post-1993 (except in the 540i), even though it is described in the owners manual. (Don't ask me why.) Removing the elapsed time function allowed the "timer" function to store 2 parked car ventilation start times. I have also experiences (in an early E32 and an E34 540i 6-speed) the timer function's "confusion" about whether it has the feature or not. Actually, the OBC motherboard has the feature, but the HVAC motherboard does or does not.
4) when you press the timer button repeatedly, does it scroll 3 messages? The LED should display "OFF Vent", "--.--t 1am", and "--.--t 2am" in succession.
5) there is a way to test whether this feature is working: With the ignition key in position "1", press the timer key to obtain the message "OFF Vent" in the LED display. While continuing to hold the timer button (and the "OFF Vent" message in the display), press the "Temp" button. (A stretch, but you can do it.)Hold BOTH buttons for 5 seconds, the release both. The LED should now display "1N Vent". Next, press the "S/R" button. A motor should whir (opening the fresh air vent)and the blower should start. Pressing the "S/R" button again will turn off the ventilation. Or, you can now remove the ignition key and either press "S/R" to turn off ventilation, or allow ventilation to continue until is shuts itself off after 15-20 minutes (I forget which).
If the test procedure doesn't work, but your heat/ac system works and the OBC works otherwise, there is probably a broken or corroded connection between the OBC and the heating/ac controller board. It mught correct itself if you remove and reintall the OBC's and the heating/ac board's connectors. If this doesn't cure it, forget about "parked car ventilation"!

As to what it's for: The obvious is to pre-cool a car which hac been sitting in the sun all day, just before you arrive to drive it home (and assuming you "punch out" at the same time each day). But it can also be activated while you're in the car. Say you'e dropping off your date at the end of an evening. Shut off the engine but activate parked car ventilation. No foggy windows!
From DPM