rear spoiler deplyment
 

I recently purchased a 2003 boxter and I would like to know how to tell if the rear spoiler is deployed

The spoiler goes up at 75mph, and goes down at 55mph. You can't really see it from in the car unless you have the sun kinda off to the back right of the car, then you can see the shadow of the wing when it goes up. If the wing fails to go up or down when it is supposed to, you will get the spoiler light on the dash that lights up when you start the car(this is the one that goes off after you drive forward a few feet). If you raise the wing manually using the rocker switch in the footwell, then it will stay up until you either lower it manually, or after you go over 75 then drop below 55 if I remember correctly.
Hope this helps.

Steve

what he said

have someone drive behind you

I think I remember seeing someone on EBay selling a LED toggle switch that would mount into the upper center console and illuminate when the rear spoiler was deployed. You may check there or go to the EBayUK site and look around. Hope that helps!