My 78 Chrysler was designed to use the AC in defrost mode even in a winter blizzard and was much more effective and drying the windshield because of it. Most heating/cooling system in cars were combined much earlier than that to take advantage of dehumidifying the air. It also has the benefit to run the compressor to keep lubrication and stop seals from drying out in the AC system that would otherwise not be used to months at a time.
There are some vehicles with separate heating and AC systems, (mainly cheap or aftermarket units) but the vast majority run together. (At least in North American cars.)
I really don’t know what to tell you there, I’m going by the vehicle manufacturer’s labels. The “defrost” mode on your climate controls (typically all the way to the right) that blows air towards your windshield will often use the ac compressor even if you have the heat set to high, because ac drys the air… it doesn’t have to be cold, it can be any temperature. Blowing wet warm air at the windshield isn’t very effective compared to dry warm air. That is especially true in our Canadian winters.
You can try it with virtually any car made from the 1970’s to today (and some in the 1950’s and 60’s) that was equipped with AC. Turn your defrost on, crank your heat, and you will hear/notice the slip clutch on the end of the AC compressor under the hood will kick in, turning on the ac unit. Some cars do come with a dedicated separate defrost button, (as opposed to the defogger button which only operates the heat lines in your back window) they also will use the AC to dry the air.
Defoggers are typically the heat lines you see in back windows, although some old cars (like my old 69 Newport) had blowers for the back window as well, and even a second heater core to feed it.
Long story short, AC is for drying air, not just cooling it.
My 78 Chrysler was designed to use the AC in defrost mode even in a winter blizzard and was much more effective and drying the windshield because of it. Most heating/cooling system in cars were combined much earlier than that to take advantage of dehumidifying the air. It also has the benefit to run the compressor to keep lubrication and stop seals from drying out in the AC system that would otherwise not be used to months at a time.
There are some vehicles with separate heating and AC systems, (mainly cheap or aftermarket units) but the vast majority run together. (At least in North American cars.)
deFROST != deFOG
I’m starting to gather that most people don’t have any clue how to properly use their environmental controls.
I really don’t know what to tell you there, I’m going by the vehicle manufacturer’s labels. The “defrost” mode on your climate controls (typically all the way to the right) that blows air towards your windshield will often use the ac compressor even if you have the heat set to high, because ac drys the air… it doesn’t have to be cold, it can be any temperature. Blowing wet warm air at the windshield isn’t very effective compared to dry warm air. That is especially true in our Canadian winters.
You can try it with virtually any car made from the 1970’s to today (and some in the 1950’s and 60’s) that was equipped with AC. Turn your defrost on, crank your heat, and you will hear/notice the slip clutch on the end of the AC compressor under the hood will kick in, turning on the ac unit. Some cars do come with a dedicated separate defrost button, (as opposed to the defogger button which only operates the heat lines in your back window) they also will use the AC to dry the air.
Defoggers are typically the heat lines you see in back windows, although some old cars (like my old 69 Newport) had blowers for the back window as well, and even a second heater core to feed it.
Long story short, AC is for drying air, not just cooling it.