Door Control - Automatic System

WARNING: This page is about a different car, the 2006 Land Rover Range Rover. However, it is still accessible from the selected car via links, so may be relevant.

The position of the ram air doors is automatically controlled by the ATC module. The positions of the recirculation doors and the distribution doors are either automatically controlled by the ATC module or manually controlled by the related switches.

Ram Air Doors

The ATC module progressively closes the ram air doors, in four steps, as vehicle speed increases, and opens them again as vehicle speed decreases. At the maximum closed position, 90% of the fresh air inlet area is closed off. A hysteresis of 15 km/h (9 mph) prevents the ram air doors from hunting at a constant vehicle speed.

Ram Air Door Positions

NOTE: A = Door position, % open; B = Opening speeds, mph (km/h); C = Closing speeds, mph (km/h)

Courtesy of JAGUAR CARS, INC.

Recirculation Doors

Unless the recirculation doors are manually selected closed, using the recirculation switch on the control panel or the steering wheel recirculation switch (where fitted), they are normally open, but automatically closed by the ATC module under certain conditions:

Rapid Cooling: For rapid cooling of the passenger compartment, when the air conditioning (A/C) system is selected on, if the driver's side reference value is less than -20% and the ambient temperature is more than 6°C (43°F), the ATC module closes the recirculation doors. The ATC module opens the recirculation doors after 12 minutes (temperate climates) or 20 minutes (hot climates), if the driver's side reference value increases to more than -5% or if the ambient temperature decreases to 6°C (43°F).

Pollution: When the ATC module detects a high level of pollutants, it sets the recirculation doors to the recirculation position for:

3 minutes if the air conditioning (A/C) system is in the heating mode.
10 minutes if the air conditioning (A/C) system is in the cooling mode.

After the recirculation time period, the ATC module returns the recirculation doors to the fresh air position. After 1 minute, if the pollutants are still present, the ATC module repeats the recirculation cycle.

Ignition Off: If the recirculation doors are in the recirculation position when the ignition is switched off, the ATC module automatically sets them to the fresh air position, to ensure that fresh air is available if a fault occurs with the recirculation door drive circuit at the next ignition on. When the ignition is switched on, the ATC module sets the recirculation doors to the position they were in at ignition off.

Distribution Doors

When a manual distribution selection is made on the control panel, the ATC module moves the distribution doors to preset positions. When the system is in the automatic mode, the ATC module uses maps of the driver's side reference value to determine the position of the distribution doors. Each distribution door has a separate map, and there are separate maps for temperate and hot climates. The mapped positions of the face level distribution doors are given a correction factor from the sunlight sensor inputs. The mapped positions of the distribution doors are overridden by special programs, as follows:

Condensation Prevention: To prevent condensation on the windshield, the ATC module closes the windshield doors for 12 seconds each time the engine starts. If a manual distribution selection is made during the 12 seconds, the windshield doors revert to normal control.

The ATC module also closes the windshield doors when the reference value is less than 90% with the recirculation doors closed and the A/C compressor disengaged.

Cold Start: When the engine starts, if the system is in the automatic mode, the driver's side reference value is 100% and the heater core temperatures is less than 30°C (86°F), the ATC module closes the face level and footwell doors and opens the windshield doors.

Duct Purging: After a cold start, if the system is in the automatic mode and the reference value is 100%, the ATC module keeps the face level doors closed until one of the heater core temperatures exceeds 60°C (140°F). The ATC module then fully opens the face level doors for 25 seconds to purge the ducts of cold air. After the purge the face level doors revert to normal automatic control. If, before or during the purge process, the reference value decreases below 100%, the ignition has been on for 15 minutes, or a manual distribution selection is made, then the purge process is cancelled.