Technical Automatic Climate Control

[ahmett]

Sorry but ACC is the easiest thing to use. set to auto, set temperature and forget. If its very cold and you want to defrost the windscreen hit the big button on the right. How difficult can it be???????

There is a lot of misinformation about AC draining HP and increasing MPG. In hot weather its cheaper to run AC than overcome the drag caused by open windows and in the winter its better to have AC than no visability as the AC keeps the windows clear. The number of numptys I see with AC fitted cars driving around with misted side windows - there is no excuse. It will also keep the seals in the compressor lubricated which means it won't need replacing (You can buy a lot of petrol for the price of a compressor ).

oh and acc uses more fuel than without, ive used acc cars many times and it always insists on having the air conditioning on when i dont need it which means more fuel used. and it also tries its hardest not to let me use recirc air, even though the air outside is full of diesel fumes that i dont want! no thank you!

 

[Mick F]

Having run a car with manual aircon for the past 13years, here in damp and dank SW UK, I feel I have some info to impart here.

Our Clio has never had the aircon turned off in all of her 95,000miles. Tell a lie - it has been turned off by the mechanics when it's been in for a service, but we've turned it on again as soon as we got her back!

Aircon is just that - aircon. Aircon can be any temp you want it to be, but the air is conditioned. ie it's dry and clean. Auto aircon is one step better.

With a manual system, you have to alter the fan speed and the temp control to maintain the required comfort level. Big deal eh? You have to alter the controls!

ACC saves you the trouble. You set the temp, and the "computer" does the rest.

What's not to like?

Regards,
Mick.

 

[Mercky]

Sorry but ACC is the easiest thing to use. set to auto, set temperature and forget. If its very cold and you want to defrost the windscreen hit the big button on the right. How difficult can it be???????

There is a lot of misinformation about AC draining HP and increasing MPG. In hot weather its cheaper to run AC than overcome the drag caused by open windows and in the winter its better to have AC than no visability as the AC keeps the windows clear. The number of numptys I see with AC fitted cars driving around with misted side windows - there is no excuse. It will also keep the seals in the compressor lubricated which means it won't need replacing (You can buy a lot of petrol for the price of a compressor ).

Glad we cleared that up! I think I can manage hitting a big button with Auto written on it! I was more referring to switching in and out of manual mode etc.

 

[Mick F]

PS.
Aircon doesn't use more fuel, you just think it does because when you turn it on, it has to do hard work. Some folk say it slows the car down when you turn it on!

If you have it on permanently, the work level is low and almost non-existant when everything's up to temp and condition.

Therefore, don't turn it off, because if you do, it will take more effort to get back to where you were.

Regards from Cornwall,
Mick.

 

[Most Easterly Pandas]

exactly. what, am i too stupid to regulate my own temperature and decide when i need ac or not?

Not saying that, but without AC activated then it can't correctly regulate lower temperatures when called upon, hence why the auto light extinguishes.

oh and acc uses more fuel than without, ive used acc cars many times and it always insists on having the air conditioning on when i dont need it which means more fuel used. and it also tries its hardest not to let me use recirc air, even though the air outside is full of diesel fumes that i dont want! no thank you!

Well it's either phscological or you've another fault with your 500 ahmett

Our Stilo with the same 1.4 16v engine as yours, which is probably 400-500kg heavier car also, uses no noticeably extra fuel with AC activated.

I want to stress again the light is AC active, not 'on' per say. Just because it's illuminated doesn't mean it's running 24/7

 

[jrkitching]

Aircon doesn't use more fuel

Sorry but this is just plain wrong.

Turning on the Aircon reduces fuel economy, in some cases by as much as 15%.

You'll likely see the greatest percentage effect when long distance cruising on hot days at modest speeds.

That's not a reason not to use it (far from it); just don't be deceived into thinking it's a free lunch.

Driving with the windows open also reduces economy by more than you might think. Above 50mph, the effect may be greater than running with A/C on & the windows shut.

 

[Most Easterly Pandas]

Sorry but this is just plain wrong.

Turning on the Aircon reduces fuel economy, in some cases by as much as 15%.

You'll likely see the greatest percentage effect when long distance cruising on hot days at modest speeds.

Well countless others and myself have found otherwise.

Even using your headlights increases fuel consumption, but it's no more crippling than using AC.

As you know I monitor my MPG rigorously in all of our vehicles, and a change in head wind will affect MPG more than using AC ever will in a modern car.

Out of interest where did 15% come from?

 

[Mercky]

So with AC or ACC on during the winter and it's kicking out heat around 21 degrees - is this using the compressor as a heat pump and as such using more fuel or is it getting 'free' heating from the engine?

 

[Most Easterly Pandas]

It'll be using is occasionally but not as much as in the summer when it's 'cooling' rather than conditioning the air.

If it's below about 3C outside the AC compressor is normally shut down completely to prevent the system from freezing over.

 

[Mick F]

The outside air is drawn in.
It passes though the cabin filter/pollen filter - call it what you will.
It then passes through the grille that is chilled by the aircon compressor. Thermostatically controlled so it doesn't freeze.
(this is the bit that people think takes loadsa power from the engine)
As it passes through the aircon grille, it is dehumidified and the moisture is collected and drained away.

The chilled and dry air then passes through the heater matrix heated by the waste heat from the engine, or is diverted via flaps away from it, or maybe mixed to a greater or lesser degree to achieve the desired temperature. This can be automatically set or manually set.

The air then passes into the passenger compartment.
It is clean, it is dry, and it is correctly set to the desired temperature, and it's a simple system.

Regards,
Mick

 

[jrkitching]

So with AC or ACC on during the winter and it's kicking out heat around 21 degrees - is this using the compressor as a heat pump and as such using more fuel or is it getting 'free' heating from the engine?

Anytime the compressor is engaged the engine is having to do more work, which has to be paid for in fuel.

The compressor is always being used as a heat pump; running in winter with the A/C on uses more waste heat from the engine (which is free) and some power to run the compressor (which isn't). The advantage is that it dehumidifies the air.

As you know I monitor my MPG rigorously in all of our vehicles, and a change in head wind will affect MPG more than using AC ever will in a modern car.

That's true.

Travelling at 50mph with a 10mph wind, aerodynamic drag is more than doubled when travelling into the wind vs travelling with the wind. I've seen out & back trip fuel figures vary by 25% on very windy days.

Out of interest where did 15% come from?

Personal observation on a long motorway journey at 50mph in summer. Trip reset each 10mi; average 73-75mpg A/C off and 61-64mpg A/C on. Quite repeatable.

At 70-75mph, the percentage difference might only be a third of that, partly because you will be using so much more fuel for propulsion at that speed, and partly because you'll get there quicker, so the A/C is running for a shorter period of time.

The more economically you are driving, the greater the percentage reduction in mpg when using A/C.

The effect is also greater on vehicles with inherently more efficient propulsion systems; using A/C in an electric vehicle will massively impact its range.

Some interesting background reading here. If you don't want to read the full article, here is one relevant quote:

" A/C accounts for perhaps 5% of total automotive fuel consumption but may use up to twice that percentage or more when turned on. And A/C impact on electric vehicle range is enormous, estimated at up to half in very hot weather"

 

[Most Easterly Pandas]

Personal observation on a long motorway journey at 50mph in summer. Trip reset each 10mi; average 73-75mpg A/C off and 61-64mpg A/C on. Quite repeatable.

Fair play, although knowing just how inaccurate the Fiat MPG trip computers can be ... :/

I just think for the benefit leaving it activated constantly, even at fuel prices today, it's not worth worrying about. But each to their own.

Luckily on the Prius AC is electric, so no power drain from the engine or overall power delivered to the wheels, all run from the hybrid battery and regenerative breaking :devil:

 

[Most Easterly Pandas]

" A/C accounts for perhaps 5% of total automotive fuel consumption but may use up to twice that percentage or more when turned on. And A/C impact on electric vehicle range is enormous, estimated at up to half in very hot weather"

[/I]

Personal experience in EV only mode it's about 10% indicated (drops estimated range as soon as ventilation system is turned on (not AC, engaging AC makes no different to estimated range), but it's a pessimistic system and always gets you further than the range says anyway by about 10-20%)

A lot of later EVs (later Nissan Leaf's for example) have heat source pumps though, beneficial in the winter, not sure on their cooking abilities though it if it's in conjunction with a traditional electric AC system.

 

[jrkitching]

Fair play, although knowing just how inaccurate the Fiat MPG trip computers can be ...

They're certainly inaccurate (real world economy is at least 5mpg less than those figures), but they are at least consistently inaccurate.

I just think for the benefit leaving it activated constantly, even at fuel prices today, it's not worth worrying about. But each to their own.

Agree completely, but if you're 'doing a Maxi' and searching for the next fuel stop with only a vague distant memory of seeing any bars on your fuel gauge, you just might want to hit the off switch .

Luckily on the Prius AC is electric, so no power drain from the engine or overall power delivered to the wheels, all run from the hybrid battery and regenerative breaking :devil:

In plug-in hybrid mode, yes - but if you're just cruising on engine power, it's likely even worse, since you also have to account for the losses to generate the electricity to power that compressor. By all accounts, Prius economy is not that great when cruising long distances at 70mph on the motorway (though I'll grant that's not the point of a Prius).

Regenerative braking is one way to use A/C to get something back - on a conventional car, you'll get a bit more engine braking when descending a steep hill if you turn the A/C up to maximum and the extra bit of cooling you get is free .

A lot of later EVs (later Nissan Leaf's for example) have heat source pumps though, beneficial in the winter, not sure on their cooking abilities though it if it's in conjunction with a traditional electric AC system.

I guess they suffer the usual problem with heat source pumps - on very cold days (when you most need them), there's not much heat to pump, and they're prone to icing in those conditions.

Air conditioners and dehumidifiers are both really just heat source pumps, the main differences being where you put the evaporator & condenser & how you direct the air.

On a conventional ICE vehicle, there's a huge source of waste heat - the exhaust; finding a way to use even a modest percentage of this could have significant economy benefits and I'm slightly surprised there hasn't been more research done in this area. Even a device which used the exhaust heat to charge the battery could get you 5-10% straight away.

 

[frupi]

Air run through the 'Air Conditioning' system is only going to be 'clean' and dehumidified correctly if the system is serviced properly at least every couple of years.

I would disagree completely with anyone who believes that any vehicle air conditioning system doesn't need servicing. The aircon system naturally loses a percentage of refrigerant year by year and the aircon dryer can become a source of bacterial build up and consequently the source of a smelly aircon system. I recently had a brand new condenser with dryer fitted and then the aircon system correctly serviced on my Saab and the difference was like night and day. The windscreen now demists and no more smelly pongs when the aircon is switched on. I use the aircon on my Saab all of the time because it comes on automatically when the engine is switched on and to be honest although the mpg reduces slightly, it is not enough to make me switch it off just to save a few pennies here and there.

As for our TA, 'er indoors uses the Automatic Climate Control system when she sees fit and doesn't have any issues with it so I can't personally understand what the gripes are from other members are. The aircon on the TA will be serviced at the two year servicing point, but not by Fiat as in my area, we are blessed with specialist aircon service technicians who just do aircon and know what they're doing.

I find it odd that many dealers never mention vehicle aircon servicing as part of any schedule. Even done outside of a dealer network at a proper specialist that does nothing else but aircon, it should only cost between £50 to £80 (dependent on the size of the car), but I guess that is a cost that is just too much for some owners.

 

[jrkitching]

...so I can't personally understand what the gripes are from other members are.

The conglomeration of actuators, flaps, ducting and various other bits of flimsy plastic have been known (though it's not that common) to misbehave.

If they do, it's a pig's ear of a job to even get at it - to work on many of the critical parts of the system, it appears most of the front interior, including at least one of the doors, has to come out, making it a difficult and expensive fix. Individual parts may be very difficult to source, and the complete unit costs a kings ransom, so if you're unfortunate enough to have problems outside of warranty, I'd say you'd likely be griping.

 

[Melanabb]

In not so distant past, people were riding smelly and slow horses. I'd rather use technology if its there (AC for example) than think of saving few pennies per litre of fuel and sweat like a pig (or freeze in winter). I might as well be riding a horse then...


Just my penny's worth...

 

[UFI]

http://www.nrel.gov/docs/fy00osti/28960.pdf

The air conditioning system is the single largest auxiliary load on a vehicle by nearly an order of magnitude.
Current air conditioning systems reduce the fuel economy of conventional vehicles, thus incremental improvements
can have a significant near-term benefit because of the large number of new cars sold each year. For high fuel
economy vehicles, current air conditioning systems have a completely unacceptable impact on fuel economy.
[B]For example, conventional air-conditioning loads can reduce EV range and HEV fuel economy by nearly 40%[/B]
depending on the size of the air-conditioner and the driving cycle

Yeah, A/C makes no difference

 

[UFI]

when you say looses last setting do you mean fan speed? Mine works fine but as MEP explained it will not return to original speed until engine has warmed back up so maybe when you went to the dealer this was the case? I regularly run mine with compressor off and air to screen but the auto functions of fan and temp still seem to work fine. If in doubt switch to Auto, set temp and leave well alone and it will do the rest! The controls can be a bit confusing until you get your head around them but then its a doddle. ACC works very well IMO.

No, it's actually faulty. First of all I run in recirc. a lot of the time which only works in manual mode (design flaw right there- unless this is another fault!). Second, it's 50-60*C in the cabin and the fan sets it self to the lowest fan speed, even if the car's only been turn off for a minute.

I have ACC in my 25 year old Skyline that blows the Fiats' away.

 

[Most Easterly Pandas]

http://www.nrel.gov/docs/fy00osti/28960.pdf

The air conditioning system is the single largest auxiliary load on a vehicle by nearly an order of magnitude.
Current air conditioning systems reduce the fuel economy of conventional vehicles, thus incremental improvements
can have a significant near-term benefit because of the large number of new cars sold each year. For high fuel
economy vehicles, current air conditioning systems have a completely unacceptable impact on fuel economy.
[B]For example, conventional air-conditioning loads can reduce EV range and HEV fuel economy by nearly 40%[/B]
depending on the size of the air-conditioner and the driving cycle

Yeah, A/C makes no difference

I see the word 'can' not 'does' - all depends upon circumstances which prevail