Air Conditioning: Overview Land Rover Discovery III

Scheme 1

Scheme 2

Description

The rear air conditioning system cools and recirculates air at the rear of the cabin. The system consists of refrigerant lines, a rear evaporator/blower assembly, a distribution system and a control panel.

Cooled air from the rear evaporator/blower assembly is supplied by the distribution system to vent outlets above each second and third row seat. The system is controlled by two switches on the control panel.

Operation

The rear A/C only operates if the front A/C is on to pump refrigerant through the rear evaporator/blower assembly. When the rear A/C switch is selected on, the indicator lamp in the switch illuminates and the rear blower relay is energized. The rear blower relay switches battery power to the blower motor, which runs at the speed selected on the blower speed switch.

The air from the blower passes through the evaporator matrix, which absorbs heat from the air. The cooled air is then supplied to the roof vents through the distribution ducts. The heat absorbed by the refrigerant in the evaporator is sensed by the thermostatic expansion valve. The thermostatic expansion valve then opens and regulates the flow of refrigerant through the evaporator in proportion to the amount of heat being absorbed from the air.

When the rear A/C switch is selected off, the blower stops. The thermostatic expansion valve senses the subsequent decrease in temperature of the refrigerant in the evaporator. The thermostatic expansion valve then closes and stops the flow of refrigerant, except for a minimal bleed flow.

Scheme 3

1. Remove dust caps from high and low pressure connectors.
2. Connect high and low pressure hoses to appropriate connections.
3. Open valves on connectors.
4. Turn valves on refrigerant station to correct positions. Operate the refrigerant station in accordance with the manufacturers instructions.
5. Turn Process switch to correct position.
6. Turn Main switch to 'ON'.
7. Allow station to recover refrigerant from system. WARNING: Refrigerant must always be recycled before re-use to ensure that the purity of the refrigerant is high enough for safe use in the air conditioning system. Recycling should always be carried out with equipment which is design certified by Underwriter Laboratory Inc. for compliance with SAE J1991. Other equipment may not recycle refrigerant to the required level of purity. A R134a Refrigerant Recovery Recycling Recharging Station must not be used with any other type of refrigerant. Refrigerant R134a from domestic and commercial sources must not be used in motor vehicle air conditioning systems.
8. Close valves on refrigerant station.
9. Turn Main switch to 'OFF'.
10. Close valves on connectors.
11. Disconnect connectors high and low pressure hoses from connectors.
12. Fit dust caps to connectors.
13. Open tap at rear of station to drain refrigerant oil.
14. Measure and record quantity of refrigerant oil recovered from system.
15. Close tap at rear of station.