If I want to turn on the heater for the front windows to defrost it - the A/C turns on automatically as well.. Why is that? should i manually turn it off or do i leave it on?

What is the background to why this is happening? I figured A/C should not be turned on (especially when its cold out).

Also, i was told to keep the AC going or crack a window for defrost the rear window faster ( while the rear button is on as well) is that true?

 

Thats normal as far as I know all cars activate the a/c to defrost the windows if you turn the a/c off you will notice that it will either not defrost at all or that alot longer to defrost the windows. Most likely due to material in the glass is the reason for it.

 

A/C stands for Air Conditioning.

What is air conditioning? It is the removal of humidity from the air.

With that being said....A/C can be COLD and A/C can be HOT!

Dont mistake the phrase " A/C " for strictly cold air....

Bottom line, you must remove the humidity from inside the car in order to defrost the windows...so therefore, leave the A/C button ON

 

The A/C functions as a dehumidifier. Cold air outside and warm air inside causes mist to form on the inside of the window so the A/C comes on to dehumidify the air and "evaporate" the mist/fog that forms on the inside of the windows on cold or rainy days.

Also, when your climate control system is set to auto, there is actually a combination of the heater and A/C working together to adjust the temperature inside the car.

David

 

Yes, it is normal for the ac compressor to come on when you turn on the defroster/heat.

I remember when I was younger and I first noticed this in a vehicle. I thought something was messed up, haha.

 

not all cars at all. ive owned 20 and the g37 is the first to do this

 

ive owned over 20 cars and driven several hundred. only the g37 does this. if it's cold out you want to heat your car, not cool it

 

You signed up just to reply to a 10+-year-old thread and offer nothing constructive?

ANY automatic climate control system is going to cycle the AC (air conditioner) compressor to adjust the temperature AND the humidity of the conditioned air. This is what helps to prevent condensation ("fogging") on the inside windows during cold, damp, and even rainy days. When it is cold outside, compressor demand is reduced as opposed to when it is hot where demand reaches 100% duty, but it will still cycle as needed to maintain conditioned air based on your temperature settings.

While cars have not adopted heat pump technology- where the AC system operates in reverse during winter months to heat homes, the compressor will still run as needed.

This feature is nothing new. Every car I have ever had over the past 30-40 years or so with a automatic climate control system behaved in the same or similar manner.

If it bothers you that much you can always press the AC button to turn the compressor OFF... eventually your windows will fog up as the interior heats up like a steam room.

Additionally, the AC compressor cycling also ensures that the oil within the refrigeration system circulates throughout keeping the seals, valves, and compressor internals lubricated.

 

The A/C compressor runs during the heat cycle as well, perfectly normal

 

Agreed with @ILM-NC G37S

Joining a forum as an adult with some car knowledge can be difficult because of the vibe that a person has to learn about each forum. With that being said you have to pay good attention to this as you start to get your count up.
It can be a bit difficult to remind yourself to look at the date stamp of each post. This is usually called "reviving" a thread and one of the unofficial rules almost EVERY forum uses is that if you are going to revive the thread it's to ask in case you're suffering from the same issue or to add to the help. Reviving old threads to share a narrow point of view just to get your counts up will irritate some folks over time.

So driving over 20 vehicles doesnt really mean much being that your argument is slightly correct if those 20 cars had more basic climate control systems. Newer cars with automatic climate controlling devices, like previously stated are made for an almost if not all FULLY automatic experience. It's been proven that the most efficient way to remove the cold humid/frost from the inside of the windows is by dry hot air. It messes with your head until you decide to properly understand it.
Your windows are foggy because too much humidity + hotter inside temps than outside. In many of these cases although the system might not turn on the AC many only let you select fresh air instead of recirculating.
Fresher air would be a bit less humid and colder and as it passes through the heater it turns into slightly drier but hotter air.

It's also a fact that older vehicles are less efficient at defrosting than auto climate control vehicles.

As an experiment you should crank up your heater to 90F and then turn the blower off in a humid event. The system will keep the vent doors usually at the last position it was at with the selected temp. You the press the fresh air button and drive around.

This lets fresh air pass through the heater unassisted, your windows will fog in a few minutes. Watch it un-fog in seconds after you properly use the system.

 

totally normal my guy