Jaguar Repair: 86 XJ6 AC Center Dashboard Vent, center flap, vacuum problem

Question
QUESTION: My AC Center Dashboard Vent does not blow no matter what switch settings I use.  Cool air does gently blow out of the L & R dash side vents.  Please advise.  Thanks

ANSWER: Hi Vance,
Set the controls to "Auto" speed control and "65" degrees on the temperature control and run for 5 minutes. The center flap should open. If it does not you either have a failed vacuum switch on the controller or a mechanical or vacuum problem with the vacuum motor at the center flap.
Howard

---------- FOLLOW-UP ----------

QUESTION: Thanks for the quick response, Howard.  I have tried adjusting the blue limiter switch (my term) under the console.  I would like it to always blow out the Center vent and stronger out the side vents.  Thanks, Vance

Answer
I am not familiar with any limit switch. The vacuum valve is on the cylinder that rotates by a small electric motor. This cylinder operates all of the vacuum valves that control all of the doors by vacuum motors. There are some electrical switches that are operated by this cylinder but they have nothing to do with the doors or the blending of the doors. The doors are only operated by the vacuum supplied by the vacuum valves. As far as I know none of the doors have any electrical components.

I do believe it is possible to change the door movements by altering the cam that operates the vacuum valves but it would be quite a job redesigning the cams.

Howard