Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Kevin Wood]

It's not clear to me if 'auto' mode runs the ac compressor when it is colder outside than you want the inside to be.

Auto (without ECO mode) runs the air con 100% of the time, IME. When the cabin requires heating it still gives the advantage of drier air.

Bear in mind that the air con has an expansion valve that controls refrigerant flow such that the air con works less hard when the incoming air is already cold, so the compressor is doing much less work when it's cold, so less fuel consumption. IME the extra fuel consumption is not noticeable anyway. I've never found a weather condition in which my air con hasn't run. I can be scraping the frost off it in the morning but I can still hear the front fans running, which means air con is engaged!

[Vamps]

Rarely use the Aircon, except giving it a run here and there, good old hot air and partially open windows works for me.

I almost always run the climate in 'AUTO'  It's there, so I use it. 

I can't see any reason not to, only occasionally and briefly I have redirected airflow to screen but still on auto, set the temperature and leave it at that.......

[dbdb]

Airconditioned air doesn't need to be cold, it can be warm too. As you say, you get warm dry air. As above, the compressor cuts out when ambient is cold to stop condensate from freezing.

As I understand it from the manual that only happens at 5C or below. So I'm guessing the compressor is running all the time above that even if you have the heater on.

[dbdb]

I don't know where you get 5-10% as a fuel burn for using aircon

I did a simple test, here http://www.omegaowners.com/forum/index.php?topic=108869.0

I believe the compressor uses between 3 & 5 HP under max load .. as my engine is capable of 217 HP, if I''m driving at 1/2 throttle thats 108 HP then 3 - 5 HP of that is certainly NOT 5-10%.

Sounds nice but I'm not sure of the logic.  Peak power on mine (V6 2.6) is 177hp at 6000 rpm.  The power curve is not linear and I normally drive at 2000 rpm so I guess I use about 50 hp with my light foot. So that's 10%,  assuming the compressor is 5HP (is it?)

Another way of looking at it is, after the aircon has been running for a while to settle down, drive at a constant throttle with the aircon ON and look at the instant fuel consumption, turn the aircon OFF and see by how much it changes ....
 

That's almost exactly what I did http://www.omegaowners.com/forum/index.php?topic=108869.0

Some years back a study was published that expounded the theory that driving with the windows open uses more fuel than the air con due to the increased drag, but I cannot prove that one way or the other.

 

Yes agree with you on that, Mythbusters did this test too, driving at speed  with the windows open is significantly bad for fuel consumption.  Worse than having the air con on when above 50 mph I think they established.  I would definitely use air con if I'm hot (or misted up), that's what its for.  I wouldn't have it on all the time though certainly not all winter.

[dbdb]

Bear in mind that the air con has an expansion valve that controls refrigerant flow such that the air con works less hard when the incoming air is already cold, so the compressor is doing much less work when it's cold, so less fuel consumption.

Thats a good point, in theory then the compressor could just be freewheeling a lot of the time.  But for that wouldn't the temperature have to be so low that the refrigerant didn't evapourate at all?  Anything above that the compressor is still having to do some compression (but I suppose not as much?).  All I can find in the manuals is that "The operation of the system is controlled by an electronic control unit, which controls the electric cooling fan and the compressor"

Haynes says "On models with Electronic Climate control, the cabin temperature is regulated automatically by a system of air valves controlled by servo motors." This make me think the cold air is just dumped if the air con and heater are on (auto mode) , rather than the compressor being relieved by refrigerent valves.

[Goldy]

Open windows uses way more fuel than air con,I tried it.

[Auto Addict]

I've found that if the pollen filter gets damp, it can cause misting up.

Before I fit a new pollen filter, I always put it in the airing cupboard overnight.

[aaronjb]

What is this aircon you all speak of?

Is it what my car should have if I ever got around to finding out where all the refrigerant escapes to?

[Clarkey]

What is this aircon you all speak of?

Is it what my car should have if I ever got around to finding out where all the refrigerant escapes to?

Yep. That would be it. My problem is that the windows seem to mist up when the heater fan kicks in. Have to turn heat and fan to max to stop windscreen misting completely. Its seems to be blowing out damp air even though the pollen filter is dry and I am not loosing coolant. Aircon compressor working at half its capacity is only reason I can think it's doing this.

[aaronjb]

FWIW mine also steams up something chronic in wet weather unless you have the demist selected more or less full time.. and I can't find any pooling water (pollen filter/scuttle drain, sunroof drains etc). I put it down to 'one of those things' - at least until such time as I fix the a/c..

[omega3000]

What is this aircon you all speak of?

Is it what my car should have if I ever got around to finding out where all the refrigerant escapes to?

+1

It must be that thing with a hole in it that went to the skip a year ago 

[Kevin Wood]

If you're having real problems with steaming up, it might be worth investigating if the recirculation flap is working OK.

[Clarkey]

Fitted a new compressor from these guys http://www.compressortech.com/index.html
No more misting up. Windows now stay clear with minimal fan speed.
Thanks for input.
James.

[cem_devecioglu]

I don't know where you get 5-10% as a fuel burn for using aircon ... I believe the compressor uses between 3 & 5 HP under max load .. as my engine is capable of 217 HP, if I''m driving at 1/2 throttle thats 108 HP then 3 - 5 HP of that is certainly NOT 5-10%.

Another way of looking at it is, after the aircon has been running for a while to settle down, drive at a constant throttle with the aircon ON and look at the instant fuel consumption, turn the aircon OFF and see by how much it changes .... very little IME.

Some years back a study was published that expounded the theory that driving with the windows open uses more fuel than the air con due to the increased drag, but I cannot prove that one way or the other.

All I know is ... air con to auto all the time .. nice and comfortable... 

yes.. I remember it..

[robson]

By that thing with a hole in it do you mean the plug at the base of the pollen filter area. I check my car for blockages here on a regular basis but yesterday opened up to put new pollen filter in and found water half way up the container. There was very little debris in the outlet and a little poke soon emptied the water. I have thought before about removing the plug and throwing it away,is there a problem in doing this.