I think we all appreciate that the Air Con in our cars needs to be used regularly throughout the year.

So, let me pose this question if I may:

I have my Climate Control set to `Auto` permanently and being as the Air Con is part of the Climate Control, does that mean that the Air Con is on all the time and therefore negates the need to use the Air Con button?

Many thanks.

Mike.

I think the aircon is only working when the aircon light is on, it comes on when you press auto but can be switched off independently from auto.

I think the aircon is only working when the aircon light is on, it comes on when you press auto but can be switched off independently from auto.

The manual states that AC is activated when the AC light is on, the engine is running, outside temp is above +2⁰ C and the blower is on.

In that case, being as the Air Con doesn't actually `condition` the air, just `cools` it...perhaps the button should be changed from `Air Con` to `Air Col` (from `Air Conditioning` to `Air Cooling`)?

Air con does condition the air, it removes moisture from it as it enters the interior. This is why its great for demisting a car interior when its wet outside, it can clear a misted screen in less than 30 seconds assuming the outside temp is over 4c.

A/C is not just about cooling the air, its possible to have heated air that has been conditioned. Basically the cool air is passed over the heater matrix heating it again.

I leave mine on all year round, very rarely switch it off.

I leave mine on all year round, very rarely switch it off.

+1

Apologies for the disjointed nature of this post, I haven't had my morning cup of tea yet and I'm typing this from memory.

The air conditioner in your car uses a variable displacement compressor. This means it can vary it's pumping capacity from 2% through to 100%. Engine load varies with pump displacement, and therefore so does fuel economy. The compressor is constantly driven by the engine and never disconnected. This is different to the old style electromagnetic-clutch compressors that are turned on and off, sometimes with a noticeable jolt, and if engaged are always working at 100%. Those of course lead to variations in vent temperature.

You should leave your aircon on all the time. Older VAG group cars used to reflect this by marking the Aircon button "Econ" and using the logic that "Econ On = Aircon-off = non-normal state so therefore light an indicator". Unfortunately drivers couldn't get their head around this so it changed recently to the logic "Aircon on = light the indicator".

Anyway, the HVAC controller (it's built into the control panel with all the aircon buttons) sets whatever amount of pump displacement it needs to achieve the target vent output temperature and humidity. If the temperature difference is high, the aircon pump is opened to 100%. If 100% is not required it's dialled back. You can see this in a measuring block (it's labelled as compressor valve voltage I think). The valve is known as a wobble valve and is basically an electromagnet driven by a PWM signal.

Leaving it on has the following benefits:

- Inhibits mould growth on the evaporator (the cold bit);

- Keeps the oil mixed with the refridgerant

- In winter it will dehumidify the air thus removing window misting very quickly

Some people say that you should keep it on/run it regularly to lubricate the seals but as far as I know this only applies to the types of aircon systems installed in the 1980s and is not true for modern systems.

Other random notes:

- The system will reduce to minimum displacement if the outside temperature is less than around 2 degrees C. This is to prevent the condenser from freezing. This is a common complaint ("My windows take forever to demist when it's really cold outside")

- The compressor displacement is also reduced under heavy acceleration, such as when the kick-down switch is activated, to enable the engine to deliver more power to the drive train.

- While there is an electric fan at the front of the car specifically for the aircon condenser, the HVAC system can also command on the main engine fan. Both fans are driven with PWM signals which means that their speed is variable. The fan speed is selected as required.

- The HVAC controller will select recirculated air when the car is in reverse gear. This is to help prevent exhaust fumes being drawn into the car. Recirc is also selected during the front windscreen washing period (i.e. water spray) to prevent smells from the water additive being drawn in.

- The HVAC sun sensor, at the centre of your dashboard under the windscreen, is actually two light sensors. One looks left and one looks right. This allows the dual-zone system to reduce the temperature on the side of the car that is exposed to sun. E.g., if the passenger is in the sun but the driver is not, the system will compensate by lowering the temperature on the passenger side.

- The centre face vents, and presumable the rear vents, are a mix of the temperature selected for the two zones. This also applies to the centre console if yours is cooled. I'm not sure if the new Skoda's (e.g. Superb) with the air vents on the B pillars for rear passengers get a true dual zone or a mix like the old system provided.

- The glove box cooling vent only blows cool air, as it takes air after the evaporator (the cold bit) but before the heater core. If the system is in heating mode, the glove box will recieve air at ambient temperature from outside the car, unless the system is in recirculate mode in which case it will recieve air at the ambient temperature inside the car.

Edited 11 December, 201213 yr by wokwon

Phew! What a comprehensive reply.

Thank you so much.

I will indeed keep my Air Con on permanently from now .

Apologies for the disjointed nature of this post, I haven't had my morning cup of tea yet and I'm typing this from memory.

........

Surely you must have had SOME caffeine in order to type in such a comprehensive explanation!?

Thanks for your effort.

Edited 12 December, 201213 yr by leWrat

Surely you must have had SOME caffeine in order to type in such a comprehensive explanation!?

Thanks for your effort.

No I'm just able to remember all sorts of useless stuff. Things I need to remember, however, seem to slip away...

Apologies for the disjointed nature of this post, I haven't had my morning cup of tea yet and I'm typing this from memory.

The air conditioner in your car uses a variable displacement compressor. This means it can vary it's pumping capacity from 2% through to 100%. Engine load varies with pump displacement, and therefore so does fuel economy. The compressor is constantly driven by the engine and never disconnected. This is different to the old style electromagnetic-clutch compressors that are turned on and off, sometimes with a noticeable jolt, and if engaged are always working at 100%. Those of course lead to variations in vent temperature.

You should leave your aircon on all the time. Older VAG group cars used to reflect this by marking the Aircon button "Econ" and using the logic that "Econ On = Aircon-off = non-normal state so therefore light an indicator". Unfortunately drivers couldn't get their head around this so it changed recently to the logic "Aircon on = light the indicator".

Anyway, the HVAC controller (it's built into the control panel with all the aircon buttons) sets whatever amount of pump displacement it needs to achieve the target vent output temperature and humidity. If the temperature difference is high, the aircon pump is opened to 100%. If 100% is not required it's dialled back. You can see this in a measuring block (it's labelled as compressor valve voltage I think). The valve is known as a wobble valve and is basically an electromagnet driven by a PWM signal.

Leaving it on has the following benefits:

- Inhibits mould growth on the evaporator (the cold bit);

- Keeps the oil mixed with the refridgerant

- In winter it will dehumidify the air thus removing window misting very quickly

Some people say that you should keep it on/run it regularly to lubricate the seals but as far as I know this only applies to the types of aircon systems installed in the 1980s and is not true for modern systems.

Other random notes:

- The system will reduce to minimum displacement if the outside temperature is less than around 2 degrees C. This is to prevent the condenser from freezing. This is a common complaint ("My windows take forever to demist when it's really cold outside")

- The compressor displacement is also reduced under heavy acceleration, such as when the kick-down switch is activated, to enable the engine to deliver more power to the drive train.

- While there is an electric fan at the front of the car specifically for the aircon condenser, the HVAC system can also command on the main engine fan. Both fans are driven with PWM signals which means that their speed is variable. The fan speed is selected as required.

- The HVAC controller will select recirculated air when the car is in reverse gear. This is to help prevent exhaust fumes being drawn into the car. Recirc is also selected during the front windscreen washing period (i.e. water spray) to prevent smells from the water additive being drawn in.

- The HVAC sun sensor, at the centre of your dashboard under the windscreen, is actually two light sensors. One looks left and one looks right. This allows the dual-zone system to reduce the temperature on the side of the car that is exposed to sun. E.g., if the passenger is in the sun but the driver is not, the system will compensate by lowering the temperature on the passenger side.

- The centre face vents, and presumable the rear vents, are a mix of the temperature selected for the two zones. This also applies to the centre console if yours is cooled. I'm not sure if the new Skoda's (e.g. Superb) with the air vents on the B pillars for rear passengers get a true dual zone or a mix like the old system provided.

- The glove box cooling vent only blows cool air, as it takes air after the evaporator (the cold bit) but before the heater core. If the system is in heating mode, the glove box will recieve air at ambient temperature from outside the car, unless the system is in recirculate mode in which case it will recieve air at the ambient temperature inside the car.

Me thinks that this is so useful and dispels so many aircon myths that there is a good case for this to be pinned in an appropriate section, mods please note. Cheers R.

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