Johnnytoxic's Winter Weather Motoring Tip

[iaind]

Wow, typical ocuk discussion here! Someone adamant they know everything, when they really don't.

Car AC systems cool the air and dry it. No heat, ever. The drying is why it helps demisting but it does nothing to aid deicing.

As for the sub zero thing, Fox is absolutely right, I'm surprised theres even a debate about it. First car I had with AC I noticed this, the AC symbol didn't come on one morning, it just flashed if I pressed the button. I thought it must be because it was too cold and sure enough it came on when the outside temp came up. It even says it in most car manuals!

 

[paddy]

From my limited experience of ground source heat pumps for house central heating, and witnessing them freeze up and stop working at -5*C, I'm with Fox, Low temps = no air con.

As for the OP:

*look out window*
*Login remotly*
*make brew*
???
Profit

+1

 

[ubersonic]

Right took a temp reading before getting in the car his morning and it was 1 degree C, got in, turned on the electrics, turned off the A/C and started the engine, then opened the bonnet, got in and pressed the screen heat button (turning the A/C on automatically) and the A/C system came on. I fully believe you that Ford A/C system my not work below 4 degrees but mine does.

I don't get why this is so hard for people to accept, an average fixed A/C system is capable of heating a room when its minus 14 outside so unless car systems are based on completely different technology I really don't see why they wouldn't be able to do their job properly :S

 

[[TW]Fox]

What car?

 

[ubersonic]

What car?

I tried to avoid this question earlier but guess it is relevant, im currently driving a BMW X5, before I get flamed id like to stress I didn't buy it, ive borrowed it from a friend for use over winter as I live in a welsh valley and snows r bad mkay, my regular car is a Honda Prelude but its in the garage atm (and off hand im sure that has working A/C below 4 degrees too).

 

[Jonnycoupe]

I don't get why this is so hard for people to accept, an average fixed A/C system is capable of heating a room when its minus 14 outside so unless car systems are based on completely different technology I really don't see why they wouldn't be able to do their job properly :S

They cant heat. Maybe cos these commercial building 'A/C' system which are really HVAC system have a HEATER? Server rooms clearly have even more requirements in terms of air quality but then generally oxygen levels dont matter too much so continous fresh air flow isnt so much of an isse. In a car fresh air is damn cold, using AC for heating would be a massive drain so the 2-3 minutes where something could be appropriate is totally disproportinate.

What technology are you trying to compare it to? I guess the one you fit but dont really know much about?

Automotive AC does its job perfectly well. Anything else would add cost and weight. No need to provide extra heat when the most the fuel you burn is waste heat.

Whilst were on the subject of AC do you know how boeing are implementing cabin air conditioning with their all electric aircraft which minimise compressor bleed? According to your suggested heating method that could just run the cold air unit in reverse....

 

[[TW]Fox]

I tried to avoid this question earlier but guess it is relevant, im currently driving a BMW X5

Which has EXACTLY the same HVAC system as my car, because the E53 X5 is effectively a 4wd E39 Touring.

My AC doesn't work when it's sub zero outside, and my AC doesn't de-ice my windscreen. Furthermore, you don't get ANY heat out of the vents until the heater matrix can supply it - usually 4-5 minutes down the road.

So now I can say with even more confidence that your AC doesn't deice your windscreen for you.

 

[ubersonic]

They cant heat. Maybe cos these commercial building 'A/C' system which are really HVAC system have a HEATER? Server rooms clearly have even more requirements in terms of air quality but then generally oxygen levels dont matter too much so continous fresh air flow isnt so much of an isse. In a car fresh air is damn cold, using AC for heating would be a massive drain so the 2-3 minutes where something could be appropriate is totally disproportinate.

Yes they can, ones such as the one in my office which I specified and our engineers installed are indeed A/C units (no fresh air ventilation involved) and are specified to be able to heat the room even when its minus 14 outside.

Which has EXACTLY the same HVAC system as my car, because the E53 X5 is effectively a 4wd E39 Touring.

My AC doesn't work when it's sub zero outside, and my AC doesn't de-ice my windscreen. Furthermore, you don't get ANY heat out of the vents until the heater matrix can supply it - usually 4-5 minutes down the road.

So now I can say with even more confidence that your AC doesn't deice your windscreen for you.

Do you think the X5 may have a problem if its bringing the A/C in at low temps then? getting worried now as I promised it would be returned tip top.

 

[mikeh501]

Interesting discussion. I've always thought that A/C helps to deice the windscreen; as back in the day without A/C it was completely impossible to deice the screen by just putting the blowers on. I know for my parents they would turn the heat up on the car, and wait for it to warm up. Nowadays people stick the "windscreen" button on, and it turns the blowers on full and engages A/C.... and somehow magically it deices the screen. Old cars without CC wouldnt do this, at least none ive every owned from more than 10 years ago. However WARM air does not come out of the vents, so I just thought it was the drying effect, but dont know how this magic deices

With regard to whether the A/C in cars that can also heat, then i've never seen one. However in building A/C, commonly referred to as HVAC systems and heat pumps its very common. Our A/C in the office can heat and cool, and there is no electric element inside or outside; it "simply" swaps the evaporator and condensor. simples, not lol.

http://en.wikipedia.org/wiki/Heat_pump

Be interested to know why car manufacturers wouldnt put a heat pump into a vehicle, rather than the simpler A/C unit? Advantages are obvious, but no idea what the practicalities are.

 

[[TW]Fox]

The reason why cars turn the Ac on when you switch the windscreen button is to de mist the screen, not to de ice it. Blowing air on it will help deice a bit but not because of the ac.

 

[Prophet]

Anyone know if the current shape Mondeo's have an Aux heater option? Mine is blowing warm air within 90 seconds of starting the car, even at -10.

 

[Jonnycoupe]

Yes they can, ones such as the one in my office which I specified and our engineers installed are indeed A/C units (no fresh air ventilation involved) and are specified to be able to heat the room even when its minus 14 outside.

But you are talking about heat pumps. Of course an environment for human occupation needs fresh air aswell.

Theres no need in a car really, in snowbelt regions you get a block heater or diesel heater. Both are cheaper than a heat pump arrangement!

Im not sure why commerical building HVAC systems are relevant to a winter car discussion either! You need to look under a bonnet, see the one compressor and two pipes, if you know AC you will know there is no way that alone can offer cabin heat.

 

[Participant]

I remember several years back going for an early morning fishing trip on a very cold morning. I got into my friend's Volvo, he started the engine and switched the aircon on...there was seemingly instant heat. I might be mis-remembering it...he may have had the engine on for ages beforehand...but I'm fairly sure we just got in it and the vent air was warm straight away.

Maybe it was a Scandinavian spec Volvo, as back then a lot of people were driving over to Sweden to buy their Volvos as it was so much cheaper.

 

[izzy eckerslike]

Why don't you use a wrap around windscreen cover, it only takes a couple of minutes to lift the wipers and lay the cover over, works a treat and cheap ones costs less than a fiver

 

[bainbridge]

In this weather its the slush on the road that gets flicked up then freezes on my windscreen which annoys me.

Last night driving home I had the heated windscreen on & blowers directing air at the windscreen but this wouldn't touch the build-up of ice, neither would the wipers, squirters were frozen solid, not just the pipes but the pumps too.

 

[paddy]

In this weather its the slush on the road that gets flicked up then freezes on my windscreen which annoys me.

It was -15*c this morning, we're a long way off slush!

 

[jamief]

In this weather its the slush on the road that gets flicked up then freezes on my windscreen which annoys me.

Last night driving home I had the heated windscreen on & blowers directing air at the windscreen but this wouldn't touch the build-up of ice, neither would the wipers, squirters were frozen solid, not just the pipes but the pumps too.

Don't drive so close to the cars in front then.

 

[ahenners]

Why don't you use a wrap around windscreen cover, it only takes a couple of minutes to lift the wipers and lay the cover over, works a treat and cheap ones costs less than a fiver

I paid a quid for mine, looks like a silver bin bag but does the trick

Usually stick the heater and back window button on first, pull the sheet off and then scrape the side windows. Within 5 mins i'm usually away.

 

[Dugganator]

I hit the demist button and watch in wonder as the car defrost in under 2 minutes.

One of the best things about the Mondeo is it's excellent aircon system.

Agreed its handy for for mondeo

 

[Overlag]

You work in the a/c industry and think car air con compressors work in sub zero temps? Fully working a/c?

Seriously?

damn I'm sorry I started this and then left you too it fox... some people huh. Comparing huge AC's for houses/offices to small basic units in cars... like... lol?