AC & heater all the windshield only (defrost) 1992 XJS coupe

Hi all:

The heater and AC blow only to defrost regardless of settings. I recall seeing a thread a few years ago but could not find it now - something to do with loss of vacuum? I assume that this vacuum line is plumbed into the engine somewhere?


Don 1992 facelift V12 + 1988 V12 coupes.

If the defrost flap cannot close, the center vent flap cannot open. They are mechanically interconnected. The defrost flap is vacuum operated thru a series of lines and a solenoid. Common for a line to become detached, or a leak to form. You have to access the actuator and check it for leaks, and check the solenoid for proper operation.

Thanks Jon - what’s the best way to access the actuator/solenoid other then turning myself into a pretzel to get under the dash? I assume that there has to be a vacuum line running from the engine but that’s not obvious to me either. Regards, Don

The solenoids and actuators are accessed under the dash by taking off the underdash and console cheek panels on each side. You need to turn into a pretzel to get to them. As i recall, the actuators for the defrost and center vent are on the right side on LHD cars.
The vacuum comes from the port on the rear left engine intake manifold. There are 3 to 4 connections there. You have to figure out which line leads to the interior.

Thanks Jon - the car is currently housed for the winter so it will be an early spring job. Don