Coolant Temperature Sensor / Switch HVAC: Description and Operation

Air Conditioning Control System


The air conditioning control system comprises relays, thermostat, pressure switches, and a control panel. Inputs from outside the air conditioning system comprise temperature information from the engine cooling system. Together these controls, in conjunction with the cooling fans, compressor clutch, blower and heater distribution and blend unit enable minimal input to maintain the required environment inside the vehicle.

When air conditioning is not selected, air is supplied by ram effect or blower to the areas selected by the controls. The air mix flap on the blend unit controls the temperature of the air being supplied. No cooled air is available.

Selecting air conditioning provides the added facility of cooled air available to be mixed as before. When required a fully cold condition can be selected by turning the temperature controls to cold, which automatically closes the heated coolant access to the heater matrix. Mixtures of cooled, fresh, and hot air can be selected to give required interior environmental conditions by selection at the control panel.

Fan timer unit
The thermostatically controlled timer will continue to operate the cooling fans after the air conditioning or ignition is switched off. When the system temperature is excessive, the fans will operate for 10 minutes to reduce condenser and underbonnet temperature.