Front Screen demist problem and no Cabin Heating

[fjmuurling]

I have a problem with the front screen demisting and the heating of the cabin.

There is no way I can get an airflow out of the 2 screen demist ventilation openings nor can I heat the cabin.

So far I have checked the following:

• vacuum hoses and assorted rubber reducers/elbows were replaced years ago by silicone vacuum tubing.
• recirclation / fresh air flap is working.
• The 2 control knobs with the 2 bowden cables are working. (when I turn them the inner parts of the cables move)
• various linkages as far as i can see (took the centre console out) are also working.
• I can see that the vacuum valve is being operated by the cam
• Coolant level is fine
• No apparant vacuum leaks (brakes are working fine).
• With the fan running I can only get air out of the cabin vents.

Can anybody tell me what is supposed to be going in the "airbox". i know there are some flaps inside but the workings (despite having the parts manual) elude me. 

Any other ideas etc are more than welcome.

[drdoom]

The vacuum motor mounted on the casing side operates the internal flap which determines whether air flows through the heater matrix, the A/C evaporator, or just out the shortcut to the face level vents. Seems you may have something impairing the actuation of this internal flap.

[Escape]

As above, it sounds like the mode flap is not doing its thing. If it remains closed, no air will flow through the heater matrix and only the cabin vents will get airflow. The mode flap is vacuum activated, by the top valve. That could be the problem or the actuator is stuck. It is described quite clearly in the workshop manual, section PD. I can send you the relevant pages in pdf if you don't have the manual.

To check the vacuum system has at least some functionality, look at the flap in the intake under the front hood. It should open when you start the engine (to generate vacuum) in all positions except off/recirc. If that is not the case, you do have a vacuum problem. If the fresh air flap moves, the problem must be limited to the mode flap. Possibly harder to get to...

 

[fjmuurling]

Thanks for the pointers.

Somehow I oversaw Section PD in the WSM . Thanks for the offer Filip, but it is in my WSM. The vacuum check with the "help" of the circ/recirc valve is an easy one in general that is wat I normally do. If that one stays open for a long time after switching of the engine than the vacuum system should have no leaks. 

[fjmuurling]

Problem solved.

It was the vacuum switch for the mode/fresh air flap wich was (slightly) out of "height" [Parts Manual 18.11A item 20]. Glued it back into the bracket (finding the right height was a bit challenging).

 

[drdoom]

Quite possibly the cause. While putting mine together it was clear that slight change of position in that bracket would kill function of the valve.

Cheers