Mondial vaccum resevoir heater system

See the figure in the "Air conditioning & windscreen defrosting" subsection in Section 2 of your OM. Item 12 is a vacuum reservoir connected by a check valve to the engine intake system (so there is always vacuum present inside regardless of the engine operating condition -- if the engine has been run recently). When you push a pushbutton on the AC pushbutton control unit, this connects and/or disconnects the vacuum inside item 12 to the various mechanical diaphragm actuators on the AC unit that move the air flaps to direct the airflow to the appropriate locations. If you run the engine and then shut it off, and then press the various AC pushbuttons, you sholud be able to hear the air flaps moving if all is OK.

 

Item 12 supplies the vacuum power for all flap movements -- so, if any are working, it is OK (and per your description of hearing some movement it seems OK). If you don't get air coming out at the windshield vents with the "windshield defrost" button pressed, the problem, most likely, is in 1) the AC pushbutton unit, 2) the vacuum hose (or its connections) connecting the AC pushbutton unit to the mech-vac actuator on the AC unit, 3) the mech-vac actuator, or 4) the corresponding flap mechanism. Good hunting!

 

Remove rear wheel on left side and also remove that wheelpanel.Underneed the coils you will see this vacuumholder. Its just a metal can (boite de conserve du Marie Thumas....).

Guido

 

The stock Mondial defroster is quite excellent when operational. When defrost is pushed, there are two vacuum acutators that must move: one to close the vent to the front dash vent, and another to open the vent to the defrost. These are items 58 and 28 in your diagram. A third vacuum actuator, item 57, controls intake from outside or recirculated air.

In addition, many Mondial owners are not aware that there are two MANUALLY operated footwell vents that are connected to the ventilation box plenum. They are two round plastic vents identical to youe dash side vents. These must also be closed to have best pressure for the defrost.

You may want to remove your plastic grill in front of the windshield to check the inlet duct and have a look-see while you are tuning up your vent system.

On modification to the system I found very helpful in a 3.2 coupe was to remove the hose to the rear seat vents (which are never used) and cap off the connection at the box. The hose basically just acts as a sink for pressure, cooling and heating, and you will find the system will now have more output at the front. I also stoppered off the side mirror defrosts at the door jambs as all they really did was leak pressure as well and did nothing to defrost the side windows.