Condenser cooling fans (Air conditioning)

Condenser cooling fans

The condenser cooling fans operate automatically whenever the air conditioning system is switched on, providing the system pressure is correct.

The cooling fans are controlled by the ECM, thermostatic switch and trinary pressure switch. If engine coolant temperature and air conditioning system pressure are normal then the cooling fans operate at low speed. If the engine coolant temperature reaches 108°C or the air conditioning refrigerant pressure exceeds 19 bar then the cooling fans will operate at high speed.

Blower control

The blower can be operated at any one of four speeds by rotating the blower switch to the required position. When the blower is switched off the air conditioning system will not operate.

The fresh air/recirculation flap has two positions and is operated by pressing the button in the centre console. In the recirculation position, air is drawn into the heater from the vehicle by closing the exterior air inlet and opening the interior inlet. In the fresh air position, air is drawn into the heater from outside the vehicle by opening the exterior air inlet and closing the interior inlet.

Heater distribution and blend unit control

Blower unit air flow, having passed through the evaporator passes into the heater unit to be heated, if required. It is then directed into the vehicle interior in accordance with the flap positions, which are designated by the air distribution control on the fascia panel.

The temperature control knob moves the heater valve, allowing engine coolant to flow through the heater matrix back to the engine when the control is moved towards the hot position. The temperature of the heated air flow into the vehicle interior is controlled by the relative movement of the heater valve.

The distribution control moves a flap which controls the direction of the air flow into the interior of the vehicle.

The face level vents have a permanent feed of heated or unheated air from the heater unit and are opened or shut by rotary thumbwheels on each face level vent.

ECM control

In addition to its various functions of controlling the air conditioning system, the ECM also controls the compressor’s clutch for system safety.

A. To protect the discharge hose material from excessive high refrigerant temperatures produced at high speed. The ECM will disengage the compressor clutch when an engine speed of 5000 rpm is reached and re-engage when the speed drops below 4900 rpm.

B. To allow more power for vehicle acceleration the compressor’s clutch is disengaged when the throttle disc angle is opened above 85°(fully open is 90°). The clutch is re-engaged when the throttle disc angle is below 80°.

C. To protect the engine’s cooling system the ECM will disengage the compressor’s clutch when the coolant temperature exceeds 117°C. The clutch re-engages when the coolant temperature drops below 112°C.