The System

All Car A/C Systems are basically similar, with a cooling capacity of almost
1-1.5 tons, in the sense that they essentially comprise:

1) An Engine Driven ‘Compressor’ with an ‘Electro-magnetic’ Clutch. The Compressor Capacity is designated in ‘CCs’, like the Engine. 80 to 120 CCs being the most popular ratings for passenger Cars of the types on our roads. The ‘Refrigerant’ used so far was ‘R-12’ of the ‘CFC’ family of gases but is now progressively replaced by ‘R-134A’, a ‘NON-CFC’, for environmental considerations.

2) A Grill-front mounted ‘Condenser’, cooled either by a common (Radiator) fan or a ’Dedicated’ fan of its own. For example Maruti 800 and Zen/Esteem – respectively. The latter is a superior and hence a more efficient but naturally a more expensive system.

3) This is followed by a ‘Receiver-Drier’, mounted somewhere in the Engine Compartment. Its purpose is to control and ‘Purify’ flow of the Refrigerant to the cooling coil, under various operating conditions.

4) A ‘Cooling Coil’ with a multi-speed Blower mounted in the Passenger Compartment, generally inside the Dashboard. This unit has two additional and vital parts viz. (a) An ‘Expansion Valve’ and (b) a ‘Thermostat’. The latter can be a ‘Bellows’ type like in the pre/EU-I M-800s or ‘Electronic’, as in the Zen/Esteem and some others. All Mpfi Cars today have the Electronic one only. Larger vehicles like the Tata Safari have two such units, one up front and the other at the rear, to cool the entire passenger area effectively.

5) The ‘Expansion Valve’ regulates the quantity of gas flow to the Cooling Coil (also called the ‘Evaporator’), depending upon the ‘Heat Load’ on it and the ‘Thermostat’ prevents ice formation on the cooling coil, which not only affects the cooling efficiency but if allowed to happen, can also damage the system.