True cost of using A/C while driving

[poppycamper]

The Evaporator. Final answer.
I had to work once with a forces "refrigeration engineer" once we called him Winco the stuff the military do is so different to commercial refrigeration he was completely useless, ringing me up constantly, nice lad though he got there in the end no offence

Oh Richard and Ann ..none taken but I could say the same about some of the civilian cowboy outfits we had to work with.
Still not, however, answered question... you say puddle on floor coming from evaporator.. so where does moisture come from if not from inside vehicle???? Are you telling me that ALL air conditioning plants are only air chillers and not as the name implies... chillers.. heaters.. AND DEHUMIDIFIERS.

 

[EuroTrotters]

This is 100% Tosh, the water drains out under the car.

It does, but some condensate* (water) can stay on the drip tray or the surface of the evaporator.

This is why, some times, after running the A/C, then Turing it off. It can fog up the screen when it starts raining for example and the windows get cold. When the fan expels the air over said evaporator up through the cars vents, the moisture (*aforementioned condensate). Can then re-condense on the now cold windows.

Simple solution, switch a/c back on again.

It will dehumidify the condensate back yet again.

 

[EuroTrotters]

It was over 30c in Manchester today.

I am off to my bed soon, room air conditioned, of course. Condensate almost like a running tap.

 

[Spawn_e_git]

Because it gets collected by the evaporator drain pan inside your dashboard and then drips out under your car onto your driveway.

So?
The inside of your doors get wet hence the drain holes in the bottom.

It does, but some condensate* (water) can stay on the drip tray or the surface of the evaporator.

This is why, some times, after running the A/C, then Turing it off. It can fog up the screen when it starts raining for example and the windows get cold. When the fan expels the air over said evaporator up through the cars vents, the moisture (*aforementioned condensate). Can then re-condense on the now cold windows.

Simple solution, switch a/c back on again.

It will dehumidify the condensate back yet again.

Most modern cars have electronic controlled vent control and close all the vents off when the engine is stopped. Never seen anything like this on any car I've had.

 

[Richard n Ann]

Oh Richard and Ann ..none taken but I could say the same about some of the civilian cowboy outfits we had to work with.
Still not, however, answered question... you say puddle on floor coming from evaporator.. so where does moisture come from if not from inside vehicle???? Are you telling me that ALL air conditioning plants are only air chillers and not as the name implies... chillers.. heaters.. AND DEHUMIDIFIERS.

Yes moisture that drips out of the car underneath comes from the air inside the vehicle, cooling air automatically dehumidifies it. Cool air can't hold as much moisture as warm air There is something we aren't communicating very well here

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[EuroTrotters]

I have 20 year old cars that do it along with my 2012 Range Rover, 2014 Sprinter.

They all do it.

Despite the electronics involved with Climate control or Semi Automatic A/C, they do not shut the air flow from flowing over the evaporator in the plenum chamber.

So, the scenario can be this.

You have had the A/C on in your car for a morning, you park up, lock up.

Come back say 30 mins later, get in your car and you've turned the A/C off. Start driving and it rains. Any condensate left on the evaporator or tray that has not drained away, can get blown up with the air onto the windows and condense.

Above scenario rarely happens in some cars, like my Wife's Audi A2, as the Climate control automatically switches the A/C on when the car is started.

BUT! IF, you switch a/c of when driving, then back on with cool windows. The same thing can happen, that is condensate on the screen or widows.

 

[Richard n Ann]

The inside of your doors get wet hence the drain holes in the bottom.

Errm yes agree

 

[EuroTrotters]

Yes moisture that drips out of the car underneath comes from the air inside the vehicle, cooling air automatically dehumidifies it. Cool air can't hold as much moisture as warm air There is something we aren't communicating very well here

And some Air Conditioners can be made to Humidify the air or dehumidify it!

<Broken link removed>

 

[EuroTrotters]

So?
The inside of your doors get wet hence the drain holes in the bottom.

Most modern cars have electronic controlled vent control and close all the vents off when the engine is stopped. Never seen anything like this on any car I've had.

I have 20 year old cars that do it along with my 2012 Range Rover, 2014 Sprinter.

They all do it.

Despite the electronics involved with Climate control or Semi Automatic A/C, they do not shut the air flow from flowing over the evaporator in the plenum chamber.

So, the scenario can be this.

You have had the A/C on in your car for a morning, you park up, lock up.

Come back say 30 mins later, get in your car and you've turned the A/C off. Start driving and it rains. Any condensate left on the evaporator or tray that has not drained away, can get blown up with the air onto the windows and condense.

Above scenario rarely happens in some cars, like my Wife's Audi A2, as the Climate control automatically switches the A/C on when the car is started.

BUT! IF, you switch a/c of when driving, then back on with cool windows. The same thing can happen, that is condensate on the screen or widows.

 

[dunnah01]

Because it gets collected by the evaporator drain pan inside your dashbo

So?
The inside of your doors get wet hence the drain holes in the bottom.

Most modern cars have electronic controlled vent control and close all the vents off when the engine is stopped. Never seen anything like this on any car I've had.

You've never had steamed up windows - you need to live more.

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[Richard n Ann]

You've never had steamed up windows - you need to live more.

I do but really try not to switch the AC on, blast it away with HEAT and it won't be there sat in the windscreen when you get back in

Anyway all this is just my opinion, when we get to our age we all do what we want enjoy!

 

[poppycamper]

I try and avoid using the AC to clear the screen, the water is quickly condensed on the coldest point (the AC evaporator in the dash) when you switch the engine off the coldest point is then usually the windscreen, and the moisture migrates to it making the problem worse when you get back in the car.
It's best to use the heater to thoroughly warm everything up, evaporate all the water and get it out of the car totally.

Yep as I said aircon with heat...... total air conditioning. Keep everything warm a

Yes moisture that drips out of the car underneath comes from the air inside the vehicle, cooling air automatically dehumidifies it. Cool air can't hold as much moisture as warm air There is something we aren't communicating very well here

Now you talkn Richard and Ann .yes apologies. You made your point and so did I.......N guess wot ..same point . Again sorry and your civilian refrig experts were not TOO bad..

 

[Spawn_e_git]

You've never had steamed up windows - you need to live more.

Of course, but long before I could afford cars with A/C, let alone Climate control....

.

 

[John Barrett]

Gosh, when I was a lad the windows steamed up for all the right reasons!

 

[kevenh]

I downsized from a car with all the bells & whistles to a little pug 108 to help get the new MH

I miss climate control and with start/stop the chance to be stationary with the engine off but ready to go when I want to go

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[tonyidle]

No.
The engine will use more fuel on the warm humid day over a cold crisp day. Therefore the use of A/C is negligible against the engines need for more fuel/Oxygen to make the same journey in the same time, hence the increase if fuel usage by the OP.

Agree about the A/C use. Why will it use more fuel on a warm humid day?

 

[dunnah01]

Agree about the A/C use. Why will it use more fuel on a warm humid day?

Something about being more dense on cold days - that's where my language starts

 

[tonyidle]

Something about being more dense on cold days - that's where my language starts

On a cold day air is more dense and, provided fuelling is adjusted, you will get more power from the engine. Conversely on a warm day air is less dense and you will get less power. But because the mixture is optimised by the engine ECU engine efficiency remains the same. So if the accelerator is adjusted to maintain a given speed fuel consumption will remain the same.

 

[poppycamper]

Agree about the A/C use. Why will it use more fuel on a warm humid day?

You have answerd your own question "warm humid day" it is trying to make a "cool unhumid day" so get a grip... spend money and be comfortable or be a miser n sweat your bollocks off.. Apologise what Is female for bollocks off ??????

 

[tonyidle]

You have answerd your own question "warm humid day" it is trying to make a "cool unhumid day" so get a grip... spend money and be comfortable or be a miser n sweat your bollocks off.. Apologise what Is female for bollocks off ??????

Think you've not read the entire post. Not that I blame you for that . We've moved slightly sideways from the AC discussion. My grip is fine and I use my aircon with no regard whatsoever for fuel use.

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[dunnah01]

On a cold day air is more dense and, provided fuelling is adjusted, you will get more power from the engine. Conversely on a warm day air is less dense and you will get less power. But because the mixture is optimised by the engine ECU engine efficiency remains the same. So if the accelerator is adjusted to maintain a given speed fuel consumption will remain the same.

Sounds a bit simplistic to me - my lambda sensor says stoichiometric is constant and it only measures unburnt oxygen so my head hurts..

 

[tonyidle]

Sounds a bit simplistic to me - my lambda sensor says stoichiometric is constant and it only measures unburnt oxygen so my head hurts..

When it's using the lambda sensor to trim fuelling (and it doesn't use it all the time) it tries to keep the lambda sensor switching at the excess/no excess oxygen point. So if it was using it when moving from hot/humid less 02 to cold/dry more 02 it would vary the fuelling to stay at that switching point.

 

[fesuvious]

3.0D Iveco N&B 2007 6tonne Flair.

Removing the air-con sent the motorway mpg (on cruise) from 18.8 to just over 20.

5% ISH.

Which is about right.
It's the extra energy used by the engine to drive the air con compressor.

 

[PeteH]

It doesn't evict all of it. The evaporating temperature of an AC is usually about 0°c, so if the system runs continuously the evap won't ice up, the water condenses onto the evap out of the atmosphere and if there is enough of it, it will drain out of the car underneath. By the time the drain starts dripping there will be plenty of water left on the evaporator and in the evaporator drain pan to cause condensation problems in the car when you stop the engine and park up.

Yes, but that volume of moisture is unlikely to be sufficient to cause issues by it`s self, It`s surely far more likely that over time the vehicle has absorbed moisture into it`s furnishings etc. and needs a proper Airing. I have had cause to put a de-humidifier in car`s, especially if they have been parked up for some time, and removed several litre of water over a couple of days. The storage "bubbles" sold in the main to the "classic" fraternity, are often coupled to a de-humidifier unit.

The humidistat on my Pressure/Temp sensor. Shows a "smiley face" between 40% and approx 60% and a "frown" out side of that!. indicating the optimum comfort level?.

 

[Spawn_e_git]

Agree about the A/C use. Why will it use more fuel on a warm humid day?

I dont think I said that. I said the air oxygen level would have an effect on the cars efficiently considerably more than the AC.
Therefore the OP's observation of a significant drop in MPG is more likely the oxygen levels in the air instead of the use of AC
I think I said "nothing to do with the A/C" in my original post but I'm not going back over this thread to check as it's gone way off topic in some areas and turned into a pissing contest on "who knows the most about A/C" in others, which for the record I only know the basics.

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[Richard n Ann]

I dont think I said that. I said the air oxygen level would have an effect on the cars efficiently considerably more than the AC.
Therefore the OP's observation of a significant drop in MPG is more likely the oxygen levels in the air instead of the use of AC
I think I said "nothing to do with the A/C" in my original post but I'm not going back over this thread to check as it's gone way off topic in some areas and turned into a pissing contest on "who knows the most about A/C" in others, which for the record I only know the basics.

As Jim has correctly said in the past the truth comes out eventually and if it has to turn into a "pissing contest" so be it

 

[tonyidle]

As Jim has correctly said in the past the truth comes out eventually and if it has to turn into a "pissing contest" so be it

Or not. My OP on this matter had nothing to do with A/C: I know as much or as little as everyone else. I was trying to correct the statement that atmospheric oxygen levels affect engine efficiency and therefore fuel consumption. They do not.

 

[Cheshirecat57]

This may be of interest ( if not, sorry- move on)

I have recently taken delivery of a fully electric Kia e-Niro

2 months in and I am surprised/happy/impressed by the accuracy of the range-ometer on the dash

Fully charged it predicts 280 miles and I am getting that will my driving style

Push the climate control button, and the range drops immediately to 270

I mainly use windows down approach, but use the button ad hoc as I need

Just info really

 

[bigtwin]

I once borrowed a small Japanese car in Qatar when my Landy broke down. When the A/C cut in it was,as if airbrakes had been engaged!

I was on a Landrover Experience day a while back and one of the things they taught/advocated was that if your off-throttle down hill speed was increasing, switch on the air-con!

Ian

 

[SpeedyDux]

This may be of interest ( if not, sorry- move on)

I have recently taken delivery of a fully electric Kia e-Niro

2 months in and I am surprised/happy/impressed by the accuracy of the range-ometer on the dash

Fully charged it predicts 280 miles and I am getting that will my driving style

Push the climate control button, and the range drops immediately to 270

I mainly use windows down approach, but use the button ad hoc as I need

Just info really

280 mile real range is very impressive. I can see why the e-Niro has a long waiting list. Climate control reducing it by about 5.7% is not much in this hot weather. Does your handbook tell you what happens to the range in winter, when you need to heat the cabin and opening the windows only freezes you faster?

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