[rich1068]

My air conditioning confuses me.

I have it set on 'AUTO' and regardless of how low I set the temperature it doesn't really seem to get that cold. The intensity of the blower seems to alter but the temperature not so much. However, if I press the cooling function on (far right, middle button) then it does get much cooler. That seems obvious but why should I have to switch that on even though the unit is set to 'AUTO'? Shouldn't that be just working anyway? The manual also says 'The cooling function is activated automatically when the AUTO button is pressed' but it obviously isn't.

Previous cars with auto air con have blown out cooler or warmer air depending on what temperature is set. This one seems to have a mind of its own.

Any thoughts?

[toxicnerve]

Someone has pressed your cooling button AFTER the auto button was pressed. This prevents it from actively cooling while in Auto.

It will cool in auto as long as the LED on the cooling button is lit.

If you press the auto button (so the system is no longer in auto) and then press it again the LED on the cooling button should light. Then, depending on the temperature you set the controls to the cooling function will be used automatically when required.

[rich1068]

Ah, that explains it. Thank you Mr Toxic.

[HighlandPete]

Originally Posted by rich1068

My air conditioning confuses me.

I have it set on 'AUTO' and regardless of how low I set the temperature it doesn't really seem to get that cold. The intensity of the blower seems to alter but the temperature not so much.

Any thoughts?

In addition to the posted comments:

Without the snowflake button illuminated, (Air Con compressor on/off switch), the cooling will be influenced by the ambient temperature. Just like any car without Air Con. If it was 5-degrees outside, you'd definitely cool down if set to 16-degrees. But if the ambient temperature is near to 16-degrees then no real cooling will take place. There has to be a decent temperature differential to get cooling without the chiller/AC function.


HighlandPete

[ghosty]

do people just leave the air compressor switched on all year round and control the temp using the climate control? as thats what i do. or do people only put it on in the summer and leave it off in the winter?

[xenon]

Always best to leave the compressor on all the time as it dries the air and it's better for the seals.

[doughboy]

+1

[ghosty]

i knew there was a good reason for it
not just for a less smelly car..

[toxicnerve]

I turn it off most of the time and only bang it on when I want active cooling. If it's cold I just let the ambient temp do it's thing.

Comes from being involved with HVAC engineering/controls I guess. When it's cold outside the air will naturally be drier anyway so no need for the compressor to dehumidify the supply air so much.

In summer it does make a big difference though and with the compressor going you get a much crisper air which is nicer to breathe!

[xenon]

I was told that leaving it on is good for the system as the recirculating refrigerant stops the seals from hardening.

[DavS1]

slightly OT, but does anyone know if the dual climate control can be synced so that when you change temp on one side the other side follows suit? instead of having to do both independantly.

[HighlandPete]

Originally Posted by xenon

I was told that leaving it on is good for the system as the recirculating refrigerant stops the seals from hardening.

Certainly needs using regularly to keep in A1 condition. Both for the mechanical parts and the smell/bacteria factor.

I leave mine on most of the time, but if it say 10 - 16 degrees and a nice dry day and I'm travelling a distance, I will switch off the compressor and let the natural air flow do the work. Saves a bit of fuel.

HighlandPete

[toxicnerve]

I'll give mine a run then

[TomF32]

This forum never ceases to amaze me! - a fountain of knowledge! Lol
Great info - I never could get my head round the auto function!
Definitely gonna do some experimenting on the way home from work now!

Thanks to all!
Tom

[rich1068]

Originally Posted by ghosty

do people just leave the air compressor switched on all year round and control the temp using the climate control? as thats what i do. or do people only put it on in the summer and leave it off in the winter?

Apart from this little glitch (now sorted, thanks all ) I've had auto air con running more or less constantly for 10 years over three cars. And I've never needed the systems re-gassing or suffered from smelly air con. I've also tested on or off vs. mpg and found negligible difference. Before my first car with air con I asked the dealer about the hit on fuel economy and he just shrugged it off as the same as cracking the window or running with a sunroof open. I've never ordered a sunroof since either.

[michaelalex17]

i always leave it on

[ASR1]

Does this really have no effect on fuel economy???

[xenon]

The compressor takes less than 1/2hp parasitic drain so I would agree that its affect on mpg is negligable and certainly way less than having to regass the a/c.

[rich1068]

My dad's car is his first with air con and our new Citroen commercial fleet have all come with it. I bang on at them to keep it running but everyone switches it off because they think a) it uses considerably more fuel and b) it's only for summer use.

[HighlandPete]

Originally Posted by xenon

The compressor takes less than 1/2hp parasitic drain so I would agree that its affect on mpg is negligable and certainly way less than having to regass the a/c.

We need to be aware that load and power demand is variable, depending on use, ambient air temperature, whether the car is baked in heat, sitting in urban traffic, etc. There is no fixed figure, so we need to see the variable demand as added to the road load in various conditions.

Testing has shown (organisations like CENERG and ADEME) a car with a small engine can have at least another 20% fuel demand when driving in hot summer conditions. Some systems even demanding up to 5hp (4kW).

Under test conditions, something like a small petrol can have a penalty of up to 4.5mpg at 30mph, and 2.7mpg at 50mph. A medium sized petrol car 3.5mpg pemalty at 30mph and 1.3mpg at 50mph.

Diesel powered cars typically have a larger mpg penalty, (percentages) at the same speeds. I know from experience my VW Passat would have a fuel penalty of 3 - 5mpg at average summer temperatures using the full climate control.

HighlandPete

[xenon]

I thought that the compressor simply had an on or an off clutch, i.e. is running or it isn't, and the temperature is blended thereafter. Unless the compressor cycles on a duty cycle or has a variable clutch then the load won't change.

[HighlandPete]

Originally Posted by xenon

I thought that the compressor simply had an on or an off clutch, i.e. is running or it isn't, and the temperature is blended thereafter. Unless the compressor cycles on a duty cycle or has a variable clutch then the load won't change.

We do have variable displacement compressors, so we do have variable loads. Working flat out to cool a car from say a peak cabin temperature of 30-degrees down a 20-degree setting, is a high demand application.

A quote, from one study.

According to the German automobile club ADAC, an additional 2.47 to 4.15 litres/100 km of fuel will be needed to cool down a car from 31°C to 22°C after its parking in the sun. After this first cool-down phase, the constantly operating Mobile Air Conditioning (MAC) will raise the fuel consumption by up to 2 litres/100 km. Depending on vehicle type and design of the cooling system this could cost the driver at least an extra €5-8 for an 8 hours' summer drive, with even higher fuel costs expected for less efficient systems and higher ambient temperatures.

HighlandPete