Don't honestly know- the car was so new I just let them take care of it. They did have to diagnose (two days) then order the part, then reschedule. I even had to wrangle with them a little over weather he could leave it wedged in the 'open' position. Come to think of it the tech used a piece of string to temporarily hold it open so my windows wouldn't fog - that kind of implies it was spring loaded, leading me to think it may be vacuum?