Car Air Conditioning.

[Malcolm Race]

Reading the posts up to this point I think that there ias some talking at cross purposes. There is air con, aka climate control and an 'air chiller' which is always working when switched on.

My mk2 Zafira has the latter (SWMBO would have liked climate control but I was not prepared to pay +£K for just that feature - others were obviously included). It is effective in summer when needed an in winter to help th demist the screen. When on it continues to cool the incoming air whatever the cabin temperature.

On the topic of incresed fuel consumption there must be a hit which I can't quantify but if I switch it on when the engine is idling, the reva drop momentarily until the ecu festores them to idle, presumably by feeding in more fuel thus having the effect of increasing fuel consumption.

Malcolm

[Bill]

In message , Adrian writes

Certainly not in either of the Skoda Octavia's I've had. Plus they demist the passenger side first. The last few years I have always had to sit waiting for the screen to clear, then at about 6.50 each morning as I drove to the paper shop, I'd regularly see another Octavia coming in the other direction with the driver frantically wiping the screen with a cloth.

According to the annual postings on a Skoda forum, others have fitted absorbent dehumidifier packs and found they help.

[Andrew Gabriel]

If you have a large engine, you probably won't notice. On my 1.4l engine, I do notice when it kicks in if I'm going uphill.

[The Natural Philosopher]

Nope.Its like the thermostat on a boiler: Once the circulating fluid is at the right temp it cuts out, even though that fluid is being pumped around a heat echanger

My jag XKs all had (massive) permanent climate control and the WHUMP of the pump cutting in at tickover practically stalled the engine - a V8 can tick over at pretty low revs.

[polygonum]

If I have understood my car's description, it positively makes the A/C pump when going downhill. And might not pump when accelerating uphill. All matter of trying to make the most efficient use of resources.

Could just be marketing puff...

[DerbyBorn]

"Richard" wrote in news:n6r0qn$12u$ [e-mail]:

It slows me down!

[Tim+]

MORE POWER!!

Tim

[Dave Plowman (News)]

Not sure about that.

'Climate control' usually means some form of integrated processor controlled air-con and heating. Set a cabin temperature and it will use either or both to achieve that.

Older air con systems were pretty well independant of the heater, although may well have a simple interlock to prevent both being hard on.

I've never heard of a car air chiller which isn't basically air-con.

[Dave Plowman (News)]

It's very noticeable on my 3.5 litre Rover too. Mostly on a hill where it will change to a lower gear when it's in operation - but not without.

It's not as noticeable on my newer BWM - but then the AC is nothing like as powerful either.

[Malcolm Race]

Dave, what I was trying to do was to was to separate the idea of climate control from what I have had in my last 3 vauvhalls - a system which when switched on cools the air coming into the car only when it is switched on.

Malcolm

[The Natural Philosopher]

I thought Labour party politics were off limits.....

[Bill]

Some years ago I had a car that when stationary the mpg reading changed to ltrs/hour. I noticed that when parked if I turned the a/c on the reading increased by 1 ltr/hour. As it didn't go to decimal places this was not all that accurate, but at least a ball park figure to think about.

[Chris French]

Our Galaxy has climate control, but you can also switch the aircon off (which of course means it doesn't cool the car if necessary, or reduce the humidity of the incoming air).

[Adrian]

Functionally, they are identical. It's just that climate control hides the functioning.

You have recirc flaps. Air coming from outside or inside?

You have an aircon evaporator. Refrigerant compressed and pumped round, chilled and dried air.

You have a heater matrix with an air flow flap. More air over the matrix, warmer air.

You have a fan. Faster, more air.

You have air direction flaps.

The air comes in from outside (or from the interior if it's in recirc), and goes over the evaporator. You now have cool, dry air. Then it goes over the matrix. You now have warm, dry air. Then it goes through the vents into the interior.

How warm? What direction? This, the control of it, is the only difference... "Trad", the driver turns the temp knob blue-red, turns the fan up or down, and the flap knob to windscreen, feet, face. Climate, the driver sets the temp and auto direction and auto fan speed.

The climate control ECU then uses internal temp sensors to decide where to direct airflow and how fast to run the fan and how much air to put over the matrix. And whether/when to have the aircon on or off.

Many climate control systems have an "ECO" button or similar - that turns the aircon off, in just the same way as turning the snowflake off on "trad" aircon. Without that mode being "on", the aircon is on all the time.

There's varying degrees of climate. Temp knob marked with numbers rather than just blue/red? There's thermostatic control with an internal temp sensor. Simple climate control.

[Adrian]

The modern compressor in the BMW will be more efficient. You could retrofit a modern one into the Rover.

[The Natural Philosopher]

a litre is about 10kwh so a litre an hour is about 10kw and with an engine efficiency of about 20% that means around 2kw ~= 3bhp to drive the pump which feels about right.

[John Rumm]

Basic air con will chill and dehumidify the air when running. That is normally before the heater matrix, so you can elect for a variable amount of heating of the dried air as well. CC just adds a closed loop element to that, where you set a desired temperature, and the car will use whatever tools are at its disposal[1] to achieve your set point.

[1] i.e. heating and air con as well as fan speed, and fresh / recirculate control.

[Chris French]

Our Diesel Galaxy (MK3, 2006 model) displays 0.2 gal/hr, which I guess is a similar litre consumption.

Turning on the air con makes no difference to this, nor does it affect the engine idle rate.

In contrast, turn on the air con in our older Mondeo made the engine idle rate drop (and you could here it as well). It also said in the manual to not have the air con on when driving up mountains, I've no idea what the Galaxy says.

[Tricky Dicky]

Our Kuga has climate control, there is a Max boost button which switches on the aircon, the heated front and back screens, turns the temp up to max. a nd the fan to max. and blasts everything at the front screen and front side windows. I got to say it's one of the most efficient systems for defrostin g and clearing the Windows.

Richard

[harry]

Air conditioning is a misnomer anyway. A proper air conditioning plant has close control over humidity. ie, Adding as well as removing water vapour from the air as needed. Something you rarely see in this country except in hospitals and manufactur ing places where close humidity control is vital.

Anything else is just air cooling/heating.