Strange Auto AC on when the heat is on

[Tacomonster]

The weather is getting colder each day as winter is fast approaching. I notice that when I turn on my heat using the fan blower, my car automatically activates the AC function. Does anyone know why? I do not have the setting for front defrost which makes me curious as to why this is. Is there a way to turn it off? I had already tried the OBDeleven to have memory hvac on and it worked for a while when the weather is warmer.

My guess is that the car knows that the weather is getting cooler and decides to kick the AC on. I heard that running the compressor when it's cold outside can hurt the system. Perhaps someone here, smarter than me can explain it?

 

[parapraxis24]

Check your manual, it should cover it. But going from memory it’s to dehumidify the cabin air.

 

[Dog Dad Wagon]

Check your manual, it should cover it. But going from memory it’s to dehumidify the cabin air.

Bingo. AC dehumidifies. When it’s cold that’s important to prevent fogging in the car

 

[VDubberinDE]

It dehumidifies but it is also how the auto temp, keeps the Temp at a steady degree.
If it just had the heat on it would have to increase and lower all the time and you would get temperature swings. With AC activated it mixes the air to the Temp you set and can keep it there with no swings.

 

[Tacomonster]

It dehumidifies but it is also how the auto temp, keeps the Temp at a steady degree.
If it just had the heat on it would have to increase and lower all the time and you would get temperature swings. With AC activated it mixes the air to the Temp you set and can keep it there with no swings.

Interesting, do you know if this applies to vehicles with manual Hvac? Mines a non auto climate control.

 

[The Fed]

Interesting, do you know if this applies to vehicles with manual Hvac? Mines a non auto climate control.

Do you have a defrost setting? I'm thinking that would answer your question.

 

[The Fed]

The weather is getting colder each day as winter is fast approaching. I notice that when I turn on my heat using the fan blower, my car automatically activates the AC function. Does anyone know why? I do not have the setting for front defrost which makes me curious as to why this is. Is there a way to turn it off? I had already tried the OBDeleven to have memory hvac on and it worked for a while when the weather is warmer.

My guess is that the car knows that the weather is getting cooler and decides to kick the AC on. I heard that running the compressor when it's cold outside can hurt the system. Perhaps someone here, smarter than me can explain it?

You can't hurt it. It runs when you use the front defrost function anyway.

 

[Tacomonster]

Do you have a defrost setting? I'm thinking that would answer your question.

I do have the front defroster but out of curiosity, why would that kick on if my setting is on the vents and not the defroster? I wonder if vw code it to automatically kick on for humidity purpose. All my other vehicles does not auto turn on ac. Instead it opens the vents.

 

[imthanick_a]

Even my 98 camry turns on the A/C when defrost is on full

 

[Tacomonster]

Even my 98 camry turns on the A/C when defrost is on full

Agreed but that’s only when the defroster is on. Mines not.

 

[Strange Mud]

where is your air flow directed? auto AC if mostly on windshield (pointing up)

 

[Tacomonster]

where is your air flow directed? auto AC if mostly on windshield (pointing up)

Front vents and feet