Hay all, I own a 1994 xjs 2+2 convertible with a 4L engine. For several months I have noticed that the climate control system has the center vent and the defogger vent modulate from one to the other every 20sec. or so. This happens no matter what the temp. setting is and if the system is in auto or manual. This happens every time the climate control is turned on. Any ideas? Thanks in advance. Fr. Rick