[HighlandPete]

Originally Posted by TMP

but, if somebody can tell me it will also make the compresser and aircon system last longer that should swing it.

Perceived wisdom is run it often, (even if not constant) same in winter, to keep the parts lubricated, and operational. Seals are less likely to leak and lose pressure, if you keep it running.

HighlandPete

[TMP]

Originally Posted by HighlandPete

Perceived wisdom is run it often, (even if not constant) same in winter, to keep the parts lubricated, and operational. Seals are less likely to leak and lose pressure, if you keep it running.

HighlandPete

Righto, both buttons will be pressed first thing. Will keep an eye on MPG over the new month.

[doughboy]

Originally Posted by chrismanchr

i run mine at 25 both sides at this time of year i like it hot that why i cant understand why it steams up

Thats absurdly hot!

You've requested 25deg but is the car actually reaching that?

Do you have all your dash vents fully open and are you sure the 'auto' LED is definitely ON?

[Martin 335d]

I'm still saying the cabin filter needs replaced, my Scania has auto climate control and as soon as it rained, I had to manually turn up the fan to keep the windows clear, replaced the cabin filter 2 months ago and it's never been off auto since, with no steamy windows.

[chrismanchr]

yes i have the vents open ,i do air the car out often ,i often drive window half open heating on full lol this may seem totally insane but its habit possibly because of my job lol but i dont have the window open when its raining

ive gone higher than 25 before now and yes the car does get there ,the heaters are very good ,and the car this moment is bathing in the sun on a cold day with rain over it from last night and no steaming up ,its only when i'm driving it ,it steams up

when i give it a good clean and hoover tomorrow ,I'll have a really good rumage and feel around see if I can see any damp patchs inside I'm still convinced theres a leak somewhere

and as for 20.5 temp how the hell can you do that youre insane ,I only do even or blocks of 5 lol

[TMP]

So aircon on first thing.

Only think i noticed, was when I got back in my car, the lower part of the windescreen misted slightly,before getting cleared (10 secs), and I do mean slightly. I can tell this is due to the aircon being on, then car being idle with mositure then staying in the system,

Now as it was a very wet day in Mcr, the question is, would I have needed aircon on or not.....

Mpg was lower than usual as well, not sure if thats due to a combination of car just been serviced, very wet road conditions, quite heavy Traffic, remap still being off. Or the Aircon

I had one other thought - if I use REST when aircon is always on, will this start misting up the car?

[Dr Dave]

AC on or off makes no difference to the fuel consumption on my 330d Tim. As has been said, the variable displacement compressor technology these days has almost but negated this effect.

[TMP]

Your probably right Dave, i am sure it was the other factors I mentioned.

Took the 5er out today, and its mpg was normal with the ac on.

[E92 325]

Originally Posted by shane55

In winter time when the cooling load in at it's absolute minimum the extra work the engine has in turning the compressor is almost unnoticeable because the compression ratio is very low. Put simply, the pressure difference between the suction and discharge side of the compressor is at its lowest, for example 2bar suction and 6bar discharge. This could be compared to inflating an empty balloon...pretty easy.

Now on the other hand in summer the work load will be triple even more than what it was in winter. Firstly the system will always have to start fully loaded...this means parked in the sun with the interior temperature in the 40's and the ambient in the 20's. In summer the compression ratio is much higher, as the system is trying to loose heat to the ambient which is much closer to the refrigerant temperature than in winter, the difference between suction and discharge pressure could be 20bar ... Now imagine yourself trying to inflate a balloon under water...not so easy eh!

Fully loaded in summer the system will consume 5 horsepower. As the interior cools down the required power needed to do the same job will fall this is somewhat due to ram air forced into the condenser at 60mph down a motorway....it's in this case the variable swash plate is great as the 5 hp demand curves off reducing fuel consumption significantly.

As said by Pete on a small car this is a lot but on a 200+hp car this is peanuts!

You a fridge or a/c eng?

[shane55]

Originally Posted by E92 325

You a fridge or a/c eng?

Yes I'm a fridgie E92 325!!!