Well here I go again, cars are equipped with a heating system and cooling system.
The heater in your car is basically a smaller version of your cooling systems radiator. Hot engine coolant is circulated through a small radiator, often times called a heater core. A fan is positioned in front of the heater core to blow cold outside air over the fins. As this air travels over the heater core, it heats up and becomes the hot air which blows out your heater vents. but Lately these cores have been replaced by an electric heating coils which heat the air faster then the heater core, but the principal of their working is same. An example of whihc I have seen was in Mitsu. Eclipse. I have not seen any other examples as I have not been in colder climates for a long time now.
Secondly the air conditioning system in your car is comprised of a compressor, condenser, expansion valve and evaporator. If you have ever used a can of compressed air to clean computer components, you will know that the bottle gets very cold in a short amount of time. This is due to the rapid expansion of the compressed gas. The same thing happens in your car’s air conditioning system. Refrigerant (AKA Freon) is compressed in the compressor and turns into a hot gas. In the condenser, this hot gas is cooled to a liquid state and travels to the expansion valve. As the Freon goes through the expansion valve it returns to a low-pressure gas and rapidly cools in the evaporator. A fan blows over the evaporator and cools the air that eventually blows out your vents.
Now there are different kind of thermostats, one equiped in a Auto climate controled cars like as @Striker mentioned in Optra and then we have the ones that come in a Rolla.
The auto climate control thermo needs proper temp to be set by the user, say we set it at 20 degrees. Now what the system does is works the compressor and tries to cool the compartment to 20degrees once this temp is attained, it tries to maintain this temp, with the help of outside air when needed to lower the temp to 20degrees. Mind you this is not hot air over the radiator or from the heater core. This is just air entering the cabin through the vents locted outside your car near the wiper blades just underneath the wind shield. As for the heating part it does the same with the heat controlling it with outside air.
In the system we have in the Rollas, there is no temp control to the precise digit, so what they have is control which turns on and off your compressor and once the compressor is on the whole system comes togather, the evaporator, condensor and compressor. Pushing refrigirent through the system. So how does the compressor turn on/off once the max cooling is reached. It has preset temp to start the compressor which can be changed using the dial on the dash which is done manually unlike the auto system. well it is not manual completely as it used to be but it is compared to the climate control systems in the Optra but that might be a cheap version too unlike the more expensive cars.
So the dial allows you to control the cooling, it does not mean the compressor will cool less but more like it will shut of the compressor sooner then previously. hence you will hear compressor truning On/Off more frequently. Again this is not controlliing the Compressor cooling but the activation of the magnetic clutch which drives the compressor with the help of the belt from the crank. So when you have it on Max cool it swtiches on/off automatically once the that temp is reached. But by you dialing it lower does not mean it will start the heater and allow hot air to come in from the radiator or anywhere else. It would allow outside air, if you choose so with the use of the button on the dash for recycling or outside air.
yes it would heat the cabin if you take the knob to the heating sde marked in red, this would still have the Compressor working and the heating on too. Coz in car without Climate control, you would have to switch off the A/c button in order fro the Compressor to be switched off.
ok I am tierd of typing and hope this helps explain few things, but there are different systems in different cars, Like I say I do not know them all I tried to make it as simple as possible.
