Air-con: recommended min usage to keep in good order.

[Burnerman]

Indeed my trip was last Thursday and Friday....naturally I didn't want to cool things down but wondered if the system was actually drying the air.
If it ever warms up - which seems unlikely - I'll test again!
South Cumbria has taken a real battering this time - I hope alls good with you!
John

 

[Peter.N.]

It depends a lot on how the vehicle is being driven, a small car on a light throttle is only using a fraction of the max engine power, especially a diesel so the impact of the aircon will be much greater, on a heavy vehicle being driven hard you probably wouldn't notice the difference.

Peter

 

[kbdiy]

"Fuel consumption not really an issue if you know how to use your right-foot properly "

You obviously pay no attention to fuel consumption.

Actually I do, which is why I said 'if you use your right foot properly'

 

[Avocet]

Indeed my trip was last Thursday and Friday....naturally I didn't want to cool things down but wondered if the system was actually drying the air.
If it ever warms up - which seems unlikely - I'll test again!
South Cumbria has taken a real battering this time - I hope alls good with you!
John

OK, that's sort of "cheating" then! Although the switch on the dash might be "on" (or, in the case of a car with climate control, it might be set to "auto"), the aircon pump itself may not actually be running. In older systems, the electromagnetic clutch on the compressor (pump) would be in series with the anti-icing switch and the dashboard switch, so when initially turned-on, the pump would run until the anti-icing switch detected an evaporator temperature of (say) 1 degree C and then it would cut the power to the pump. Air coming through the evaporator and into the cabin would then warm it up until it got to(say) 5 degrees, at which point the anti-icing switch would allow power back to the electromagnetic clutch and the pump would run again until it got back down to 1 degree...and so on. It follows that if the ambient temperature was 0 degrees, your pump would never actually cut-in. More modern systems are more sophisticated, but they all still contain some feature to prevent ice forming on the evaporator fins and stopping air passing through it and into the cabin. If the pump wasn't running, it wouldn't have been dehumidifying the air (but then again, it wouldn't need to because air at 0 degrees can't hold that much moisture anyway)! Air at (say) 10 degrees is still pretty cold, but the pump would then run and bring it down to 1 degree (to get most of the moisture out of it) before passing it through the heater matrix to warm it up again.

We're lucky on the West side of Cumbria (or the "Cumbrian Riviera" as we like to call it) because it's all coming from the EAST. Still snow on the fell tops and some of the fields, but roads are clear round me (for now)!

 

[Avocet]

It depends a lot on how the vehicle is being driven, a small car on a light throttle is only using a fraction of the max engine power, especially a diesel so the impact of the aircon will be much greater, on a heavy vehicle being driven hard you probably wouldn't notice the difference.

Peter

I agree - although cabin volume and glass area has a lot to do with it too. Something like a V12 Aston with a small cabin and not much glass area won't need much of an aircon pump to keep the cabin cool and the parasitic losses of the aircon pump would be a drop in the ocean to a huge petrol engine at part-throttle. On the other hand, an underpowered diesel MPV with a big cabin volume, lots of glass and not much engine would need a much bigger pump to keep it's interior cool - the engine would practically stall when the aircon pump cut-in! (if it wasn't for the idle speed control)!

It's part of the reason why I hate these stupid "sound bite" assertions like "aircon adds another 7% to your fuel consumption" because it varies wildly depending on a number of different circumstances!

 

[mointainwalker]

[/quote]It's part of the reason why I hate these stupid "sound bite" assertions like "aircon adds another 7% to your fuel consumption

Yes, Avocet, but in a general "Save fuel " article they are useful as they give a vague notion of how much fuel you are wastiing and equally whether you ought to concern yourself first with :

a) The bike-carrier
b) The air-con
c) Open windows and the dog sticking its head out.

Even though all of these are obviously variable by car/dog. [/url]

 

[Avocet]

...but that's the trouble! They're are so inaccurate that they DON'T allow you to make that judgement!

 

[mointainwalker]

Hello John/Burnerman


Just wondered if the warmer weather had allowed you to undertake any comparative a/c on/off journeys ?

 

[Burnerman]

Hi Mr. Mointainwalker
I'm afraid sensible air con testing is still out of the question here.....its only getting up to 11 deg C at the moment!
John

 

[mointainwalker]

11 C ! Luxury, pure luxury