Automotice air conditioning control

I understand the basics, but I don't understand what the temperature control does in the car's passenger compartment. It seems to regulate the cold air output, so I doubt that it is a thermostat. Can anyone explain and does it control the output of the compressor?

Thanks,

Reply to
Dave
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In most cars, the compressor is controlled by a thermostat buried inside the evaporator coils in the dashboard. This thermostat usually set to keep those coils a few degrees above freezing- 38 to 40 degrees Farenheit (some cars use an evaporator pressure regulator valve instead of cycling the compressor at all, still others use variable-displacement compressors).

The cabin temperature control blends warm air from the heater core back in with the cold air from the AC evaporator core. The reason this is done is to maintain a fairly constant air temperature out of the AC vents. Car air conditioning is normally a "one pass" system where the air is taken in from outdoors, cooled/dehumidified by the AC, re-warmed (if necessary), and blown into the cabin so that any exhaust and fuel fumes are forced out constantly (except on "recirc" or "Max" ac settings, and even then there is a good percentage of fresh air dilution). If the system cycled the compressor to maintain cabin temperature, the air blowing out of the vents would constantly be swinging from uncomfortably warm and humid (outside air temp) to cold and dry (38-40 degrees F) every time the compressor cycled.

Reply to
Steve

Reply to
ROY BRAGG

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