Main scheme

The Defroster is connected to the bus engine cooling circuit. The hot fluid passes through the Defroster radiator and returns to the engine.
The blowers take the cold air and blow it through the radiator so that the heated air is passed to the driver’s area and onto the windscreen.
The amount of refrigerant passing through the Defroster is regulated by a valve or tap which can be controlled manually, although it is usually controlled electronically.
Likewise, the volume of air can be controlled over a number of speed steps or progressively.
If it is necessary to cool the driver’s area instead of heating it, the Defroster can be connected to the vehicle’s air-conditioning unit (usually mounted in the roof) by means of a refrigerating gas pipe running to the evaporator installed in the Defroster. The refrigerant circulates through the evaporator and from there returns to the air-conditioning unit compressor.

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