[vikram_d]

Originally Posted by sarathlal

maintaining a set temperature by using the hot/cold air mix, apart from other parameters like blower speed.

It's not that simple. There are a number of other factors also that the climate control ECU takes into consideration like outside temperature, amount of sunlight hitting the light sensor which is normally placed just behind the front windshield and inside temperature. Based on all these inputs it decides what mix of hot/cold air and blower speed it needs to maintain to regulate the temperature to user desired levels.

This logic also decides whether it switches on in fresh air mode or recirculation mode.

A simple example to test this logic is to park your car in the sun for about an hour and switch on climate control. Set temperature to around 21 degrees before you park the car. You will notice that it will switch on recirculation mode 95% of the times. Do the same experiment on a cool night or a cloudy/rainy day and at the same temperature the AC will switch on in fresh air mode.

[sarathlal]

Originally Posted by vikram_d

It's not that simple. There are a number of other factors also that the climate control ECU takes into consideration like outside temperature, amount of sunlight hitting the light sensor which is normally placed just behind the front windshield and inside temperature.

Thanks, and also found this article on net, which describes the cooling mechanism. Interesting to see how the 'heater' component actually works. This would mean that, by opening up the heater, we are just using the available heat from engine and no extra effort used like for cooling.

http://auto.howstuffworks.com/cooling-system2.htm

[vikram_d]

Originally Posted by sarathlal

Thanks, and also found this article on net, which describes the cooling mechanism. Interesting to see how the 'heater' component actually works. This would mean that, by opening up the heater, we are just using the available heat from engine and no extra effort used like for cooling.

http://auto.howstuffworks.com/cooling-system2.htm

Yes normally heating systems on automobiles run on engine coolant which is hot and by this logic running your car's heater on permanently should give you theoretical mileage benefits as the engine runs cooler when the heater in on.

[amitpunjani]

In my Sx4 Zdi, the compressor cut off time is only 8-10 sec, irrespective of the outside temp.

For e.g. outside temp is 23 C, and i set the temp at 25 C, ideally the compressor should cut off for longer duration ( as in the case of room aircon) but in this case, whether i set the temp at 27 or 26, the compressor will only cut off for 8 to 10 seconds and will mix warm air

This kinda of arrangement doesn't really help in fuel saving advantage.

Is this a problem or normal within all the ACC cars?

Amit

[freedom]

@Mods I don't know if this is the right thread.

I would like to know what is the ideal temperature that you set on ACC?

I find 23-24 the ideal spot. What about you?

[alpha1]

Originally Posted by freedom

@Mods I don't know if this is the right thread.

I would like to know what is the ideal temperature that you set on ACC?

I find 23-24 the ideal spot. What about you?

You are right.
Refer the attached psychrometric chart that is used to design the HVAC (heating, ventilation, air conditioning systems).
There are two colored areas that are summer comfort zone and winter comfort zone.
The only reason why winter comfort zone exists separately from the summer's is because during winters people wear heavy insulating clothing and thus would feel warm if keeping the temperature according to the summers.

So what does it say?
When wearing summer clothing: Temp 23 to 27
When wearing winter clothing: Temp 20 to 24
Of course there are things like humidity etc but you needn't bother - hopefully the person designing your air conditioner has taken care to ensure that RH lies in the 30% to 60% range most of the times when AC is in operation.

Anyone preferring lower temperature while wearing light clothes needs to get his blood test done. Usually when cholesterol levels are high along with high blood sugar (check the postprandial, not the fasted), the blood circulation to the extremities (fingers, toes, nose etc) reduces, less heat is dissipated, and thus a person feels more "hot".

[Ashokkp]

Hi

The Climatronics A/c on my Skoda Octavia does not allow "recirculation" on AUTO. In the humid and dusty environs of Mumbai, what's the point of driving around in FRESH AIR mode? What's the logic behind this restriction OR is it a malfunction to be rectified?

Regards
Ashok

[castiel]

Originally Posted by alpha1

Anyone preferring lower temperature while wearing light clothes needs to get his blood test done. Usually when cholesterol levels are high along with high blood sugar (check the postprandial, not the fasted), the blood circulation to the extremities (fingers, toes, nose etc) reduces, less heat is dissipated, and thus a person feels more "hot".

I didn't knew that.Thank you alpha1.
I am feeling always hot and I have reasonably high cholesterol. Fasting sugar is okay but never tested the other one. I will do it next time.
I am setting 20 or lower in ACC whenever i am in a car and I dont wear warm clothes unless the ambient is less than 15C

[alpha1]

Originally Posted by castiel

I didn't knew that.Thank you alpha1.
I am feeling always hot and I have reasonably high cholesterol. Fasting sugar is okay but never tested the other one. I will do it next time.
I am setting 20 or lower in ACC whenever i am in a car and I dont wear warm clothes unless the ambient is less than 15C

There is a more benign possibility that your metabolism is high and that causes you to feel more "heat".

[anuragn]

Originally Posted by Ashokkp

Hi

The Climatronics A/c on my Skoda Octavia does not allow "recirculation" on AUTO. In the humid and dusty environs of Mumbai, what's the point of driving around in FRESH AIR mode? What's the logic behind this restriction OR is it a malfunction to be rectified?

It looks like a malfunction to me. My Rapid does allow to choose recirculation on AUTO (it's a climatronic a/c).

[pixantz]

Originally Posted by Ashokkp

Hi



The Climatronics A/c on my Skoda Octavia does not allow "recirculation" on AUTO. In the humid and dusty environs of Mumbai, what's the point of driving around in FRESH AIR mode? What's the logic behind this restriction OR is it a malfunction to be rectified?



Regards

Ashok

Mostly it depends on what temp you have chosen. Most acc switch to fresh air automatically if the desired temp is selected more than around 20deg. The point is, are you feeling comfortable? If not try lowering the temp setting and check. Also manually select recirculating mode and then press auto and see if it stays. Some ACC systems allow you to choose the fan speed and circulation mode upto an extent on auto mode too. The key is your choice of cabin temp. All ACCs have slightly different working philosophies according to the Manufacturer preferences/settings.

[Ashokkp]

Hello Pix

I checked. Irrespective of the temperature setting, the system does not allow RE-CIRCULATION on AUTO.

It does achieve comfortable temperatures in MANUAL mode, but this anomaly prevents me in utilizing the real benefit of Climatronics- I need to operate only on manual mode to recirculate.

How to correct this?

Regards
Ashok

[freedom]

Originally Posted by Ashokkp

I checked. Irrespective of the temperature setting, the system does not allow RE-CIRCULATION on AUTO.

In Polo GT I can switch the re circulation to on/off and still the Auto mode doesn't get reset to manual. I drive with AC set to something between 22 and 24.

Post this query on Octavia review/ownership threads to get the owners to check and confirm it.

Also get it checked with A$$.

[pixantz]

Originally Posted by Ashokkp

Hello Pix

I checked. Irrespective of the temperature setting, the system does not allow RE-CIRCULATION on AUTO. How to correct this?

Regards
Ashok

Originally Posted by freedom

In Polo GT I can switch the re circulation to on/off and still the Auto mode doesn't get reset to manual.

Ashoka, as you have seen, 'freedom' is able to switch to recirculate mode in ACC whilst you can't. This mostly points out to a software bug/glitch. What you require is a software update. Show the vehicle to ASS and ask them to get the latest update done on your car. Also surely share the malfunction issue. All the best.

[vikred]

I don't think there would be any difference between FE of cars with manual and automatic ACs. AC compressor acts as a parasite on the engine belt. If the AC is switched on, it is switched on. The compressor is the only component which acts as a load on the engine, which is the reason why FE drops when AC is used.

In manual, there is no thermostat. The blue-red temperature knob is only used to control the mix of hot (from the heater core. Google it!) and cold air (from the evaporator) to blast air into the cabin.

In the ACC, however, there is a temperature sensor mostly near the dashboard itself (for minimise cost) that varies the hot-cold mix and fan speed to achieve and maintain the desired temperature. The ACC may also change other params like AC recirculation, etc., but that's about it.