Author Topic: Hot weather and aircon.  (Read 3527 times)

VicW

  • Approved Member
  • *
  • Posts: 1441
  • Country: england
  • My Honda: 07 Plate Civic 1.8 i-Shift.
Hot weather and aircon.
« on: July 23, 2018, 03:14:31 PM »
I am very surprised at the number of cars that you know have aircon are driving around in the current weather conditions with their windows open.
This does not help the aircon work at all, hot air flows into the car and negates anything that the aircon is trying to achieve.You may feel a breeze on your right shoulder and the right side of your face but the rest of the car is hot
If you believe that using the aircon seriously affects your fuel consumption then driving with the windows open will affect it even more than the aircon will.

Vic

culzean

  • Approved Member
  • *
  • Posts: 8017
  • Country: england
Re: Hot weather and aircon.
« Reply #1 on: July 23, 2018, 04:39:15 PM »
I am very surprised at the number of cars that you know have aircon are driving around in the current weather conditions with their windows open.
This does not help the aircon work at all, hot air flows into the car and negates anything that the aircon is trying to achieve.You may feel a breeze on your right shoulder and the right side of your face but the rest of the car is hot
If you believe that using the aircon seriously affects your fuel consumption then driving with the windows open will affect it even more than the aircon will.

Vic

Maybe they have aircon fitted but it is not working - just like hot weather kills your battery and cold weather finds out it is dead,  many people do not use aircon in winter / cooler weather and when they come to use it in hot weather it does not work.   We had the aircon clutch on Civic fail during the journey home from South Wales - quite common on Civic apparently the energising coil fails - a real PITA of a job as front drivers side wheel underguarding, screenwash reservoir and bumper need to come off for access (clutch assembly is held together with 2 large external circlips buried deep inside assembly).

For anyone interested have attached PDF photos of the way clutch is built up,  I feel that original clutch design left something to be desired (not made by Honda, they use Sanden clutch assemblies) as the clutch plate was hardly contacting moving pulley where it should (on the face of outer spring loaded plate - which is all rusted up) and seemed to be contacting only in the centre which is all shiny and scored) - I don't know if it is the clutch slipping and overheating that caused the coil to fail,  but I replaced the whole assembly and the new one had a different design of clutch plate and the area of pulley where clutch plate sits was totally flat and did not have the raised circumferential part that was stopping old plate contacting fully.

A good learning excercise... new clutch cost £55 including delivery.
« Last Edit: July 23, 2018, 05:05:11 PM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

VicW

  • Topic Starter
  • Approved Member
  • *
  • Posts: 1441
  • Country: england
  • My Honda: 07 Plate Civic 1.8 i-Shift.
Re: Hot weather and aircon.
« Reply #2 on: July 23, 2018, 06:50:56 PM »
Many of the cars I am referring to are very new Range Rovers, Jaguars, BMW's and Mercedes.

Vic.

guest7281

  • Guest
Re: Hot weather and aircon.
« Reply #3 on: July 23, 2018, 08:04:11 PM »
I know a number of people who never switch on their aircon because they believe it uses a lot of extra fuel, and almost all of them then find it no longer works when they do, which of course hurts them even more in the pocket when they come to sell....personally I leave mine on all the time as it also helps avoid steaming up in cold weather.


Jocko

  • Approved Member
  • *
  • Posts: 9356
  • Country: scotland
  • Fuel economy:
  • My Honda: Died from rust.
Re: Hot weather and aircon.
« Reply #4 on: July 23, 2018, 08:23:59 PM »
I used to leave mine on constantly. On a warm humid day condensation would form on the outside of the windscreen, just above the vents. That was the best check it was working.
I tried fuel consumption figures with air con and without, and the difference was lost in the scatter of figures. Nothing that was worth the worrying about.
The car (Volvo S40) had 48K miles and was 6 year old when I bought it. I sold it 10 years later with 131K miles on the clock and the air con worked flawlessly, summer and winter, for the entire time I had it (other than the couple of top ups I tried with it off).
The car also had a sunroof, but it was kept shut, with the blind across, for the entire time I had it. Personally, I think a sunroof is just a waste of money. On a car without air con it can be nice to tilt the sunroof on a warm day, but opening it just lets the sun bake the top of your head!

plasma

  • Approved Member
  • *
  • Posts: 200
  • Country: england
  • My Honda: 2023 mark 4
Re: Hot weather and aircon.
« Reply #5 on: July 24, 2018, 09:26:58 AM »
I know a number of people who never switch on their aircon because they believe it uses a lot of extra fuel, and almost all of them then find it no longer works when they do, which of course hurts them even more in the pocket when they come to sell....personally I leave mine on all the time as it also helps avoid steaming up in cold weather.


+1, yes I do the same,on all the time.


Plasma.

peteo48

  • Approved Member
  • *
  • Posts: 2689
  • Country: gb
  • I have entered the Jazz Age
  • Fuel economy:
  • My Honda: 2021 Honda Jazz Mk4 1.5 i-MMD EX
Re: Hot weather and aircon.
« Reply #6 on: July 24, 2018, 10:26:11 AM »
I have aircon and it works. I often prefer the draft from open windows. That said, if I'm on the motorway and it's warm outside, I'll always have it on.

culzean

  • Approved Member
  • *
  • Posts: 8017
  • Country: england
Re: Hot weather and aircon.
« Reply #7 on: July 24, 2018, 10:56:09 AM »
I have aircon and it works. I often prefer the draft from open windows. That said, if I'm on the motorway and it's warm outside, I'll always have it on.

For hay fever sufferers cabin filter / aircon is a blessing, but i only have it on low fan and a fairly high (20 deg) rather than super cold setting otherwise it can dry your sinuses on longer journeys and cause other problems. the general rule is below 30 mph the drag loss form open windows will be less than power aircon uses,  above that speed better to close windows and use aircon.
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

Jocko

  • Approved Member
  • *
  • Posts: 9356
  • Country: scotland
  • Fuel economy:
  • My Honda: Died from rust.
Re: Hot weather and aircon.
« Reply #8 on: July 24, 2018, 11:27:00 AM »
the general rule is below 30 mph the drag loss form open windows will be less than power aircon uses
The figure I have seen most often is 50 mph but I get narked with my navigator if she opens a window at any speed. I let her off when we first start off as the air coming through the vents could be from an oven, but once it drops to ambient I like the windows closed.

jazzway

  • Approved Member
  • *
  • Posts: 327
  • Country: nl
  • Fuel economy:
  • My Honda: 2010 — 1.4 iShift Elegance — Storm Silver — GG3 L13Z2 3rd gen.
Re: Hot weather and aircon.
« Reply #9 on: July 24, 2018, 03:06:23 PM »
.... You may feel a breeze on your right shoulder and the right side of your face but the rest of the car is hot
...
Vic
You must be joking. ;) The breeze when it is 35C outside is not something i want on my left shoulder and face. haha.

Climate control at 21, not lower because of the difference when i step out of the car.
Btw, it’s on here year round.

peteo48

  • Approved Member
  • *
  • Posts: 2689
  • Country: gb
  • I have entered the Jazz Age
  • Fuel economy:
  • My Honda: 2021 Honda Jazz Mk4 1.5 i-MMD EX
Re: Hot weather and aircon.
« Reply #10 on: July 24, 2018, 05:03:16 PM »

I tried fuel consumption figures with air con and without, and the difference was lost in the scatter of figures. Nothing that was worth the worrying about.
The car (Volvo S40) had 48K miles and was 6 year old when I bought it. I sold it 10 years later with 131K miles on the clock and the air con worked flawlessly, summer and winter, for the entire time I had it (other than the couple of top ups I tried with it off).


I think I agree that the aircon is not the massive drain you sometimes read about - yes it will use more fuel but I've seen figures of 10% bandied about and I don't believe them.

culzean

  • Approved Member
  • *
  • Posts: 8017
  • Country: england
Re: Hot weather and aircon.
« Reply #11 on: July 24, 2018, 05:45:10 PM »
.... You may feel a breeze on your right shoulder and the right side of your face but the rest of the car is hot
...
Vic
You must be joking. ;) The breeze when it is 35C outside is not something i want on my left shoulder and face. haha.

Climate control at 21, not lower because of the difference when i step out of the car.
Btw, it’s on here year round.

I rarely use climate control because it blows out of the wrong holes (for me anyway) and sometimes the fan almost goes off altogether,  I use normal aircon and like to manually decide which vents to use,  will sometimes turn temperature down to 16 and select recirculation if car has been in the sun,  but after about 5 mins I will put it back on fresh air and 20 degrees,  which is where it normally is.  If I have rear seat passengers I will use centre dash vents (still blows out of side dash vents) and angle them to blow upwards into rear of car with fan speed up quite high to quickly get some cool air into rear of car for them.  The lower the set temperature  on aircon the more fuel it uses anyway because compressor run time will be longer,  I think 20 deg keeps car cool enough an more importantly takes the nasty humidity out of the air, which makes it more comfortable anyway.
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

VicW

  • Topic Starter
  • Approved Member
  • *
  • Posts: 1441
  • Country: england
  • My Honda: 07 Plate Civic 1.8 i-Shift.
Re: Hot weather and aircon.
« Reply #12 on: July 24, 2018, 07:33:04 PM »
The lower the set temperature  on aircon the more fuel it uses anyway because compressor run time will be longer, 
The air temperature in the car is arrived at by mixing hot and cold air whether it's climate control or manual. The AC compressor runs for long enough to turn the cold gas back to a hot liquid before it shuts off, this is a cycling period of about eight seconds on and off.
The hot liquid is cooled first at the condensor at the front of the car before going through a pressure reducing system where it turns back to a cold gas before passing through the evaporator forward of the dashboard to provide a cold air source which is mixed with air from the heater system to provide air at the selected temperature
With climate control this is done automatically, with a manual system the temperature  is controlled by the heater temperature setting.

Vic.

culzean

  • Approved Member
  • *
  • Posts: 8017
  • Country: england
Re: Hot weather and aircon.
« Reply #13 on: July 24, 2018, 08:44:43 PM »
The lower the set temperature  on aircon the more fuel it uses anyway because compressor run time will be longer, 
The air temperature in the car is arrived at by mixing hot and cold air whether it's climate control or manual. The AC compressor runs for long enough to turn the cold gas back to a hot liquid before it shuts off, this is a cycling period of about eight seconds on and off.
The hot liquid is cooled first at the condensor at the front of the car before going through a pressure reducing system where it turns back to a cold gas before passing through the evaporator forward of the dashboard to provide a cold air source which is mixed with air from the heater system to provide air at the selected temperature
With climate control this is done automatically, with a manual system the temperature  is controlled by the heater temperature setting.

Vic.

System uses pressure of gas to control clutch, when system has not been run the gas pressure on the low and high side of compressor will be the same high pressure  when the compressor is engaged  and starts pumping gas around the system the low side system pressure drops as gas liquifies and rises on high side and at a certain point low side pressure will drop low enough to trigger pressure switch and compressor clutch will disengage,  as gas warms up system pressure rises and compressor clutch will energise .   

There will be no need to use any warm air from heater system when outside temp is 30 deg and inside temp is 21, just the normal incoming hot air will do, no sense in adding more heat to air that is already hotter than you need.   Once the interior of the car gets to set temp the temp control should no longer energise the compressor fan - this will happen sooner if temp is set nearer to ambient, obviously the lower the set temp the longer the aircon compressor will have to run in total on any journey because the lower the set temp the quicker the interior of the car will warm up again past the setpoint and require compressor to run again.  The compressor is only drawing power from engine when it is running (also when the compressor runs the aircon fans on both radiators will need to run and they draw quite a few amps as well).
« Last Edit: July 24, 2018, 08:59:24 PM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

Tags:
 

Back to top