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Old 17th April 2007, 23:59   #1
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Default Airconditioning cars, were we fooled?

after looking at climate control system in new generation cars, while driving my baleno i notice this thing...airconditioning cools well no doubt, thats why i reduce the cooling and keep the temperature lever in middle. but what is actually happening, i am adding hot air and the ac compressor is running all the time? it is trying to cool the thermostat but the cabin is being heated by warmer air. so milage drops more if the ac selection is not in full cold?

i want to avoid this, if this is the fact. experts comment.
want to put in a thermostat or thermister control on the compressor. thermostat i got in market it comes for about 250rs, but astetically not good looking with its thick probe. can anyone give me design of a thermister controlled relay diagram. i want to try out this and if all goes well i will be able to improve milage with ac on.
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Old 18th April 2007, 00:34   #2
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Originally Posted by gigy View Post
airconditioning cools well no doubt, thats why i reduce the cooling and keep the temperature lever in middle. but what is actually happening, i am adding hot air and the ac compressor is running all the time? .
could you clarify that?
as i understand it adjusting the cooling setting on the aircon saves fuel.the thermostat trips the compressor once the desired level of cooling is reached...
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Old 18th April 2007, 11:20   #3
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adjusting the level only opens the flap valve allowing in hot air. it does not adjust the thermostst. i dint find any link on the lever. so the compressor keeps running all the time.
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Old 18th April 2007, 11:25   #4
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adjusting the level only opens the flap valve allowing in hot air. it does not adjust the thermostat. i dint find any link on the lever. so the compressor keeps running all the time.
Now this is news for me. Why would they do that when a thermostat is pretty cheap to install. Experts please comment
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Old 18th April 2007, 11:28   #5
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well. A thermostat for a particular temperature is cheap. But, now, you want a thermostat which can cut off at different temperatures based on a dashboard control. This is expensive. Thats what climate control is all about..

If anyone has an inexpensive way to add climate control - i am intersted to try it.
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Old 18th April 2007, 11:34   #6
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experts will be able to explain this. i didnt find any in my old esteem, neither could i find it in 2k model baleno. i didnt find any connection from the temperature control slider to the thermostat. are they missing in my car? thats why thinking of designing a thermostat setup so that i can control the grill air temperature and cut off compressor economically rather than adding hot air but keeping compressor all time..
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Old 18th April 2007, 11:50   #7
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Did you seriuosly believe that the blue red knob controls the temp ? i have my doubts about that, i have never used that to reduce cooling (Do i have to, in chennai). I think this was seriously discussed in a thread here.

http://www.team-bhp.com/forum/techni...d-start-5.html
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Old 18th April 2007, 12:41   #8
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Originally Posted by gigy View Post
adjusting the level only opens the flap valve allowing in hot air. it does not adjust the thermostst. i dint find any link on the lever. so the compressor keeps running all the time.

Perhaps your lever is not doing what it is intended to do. In my 7 year old Zen, I can hear the compressor cut out, with a distinct click. And it cuts out sooner, if I keep the thermostat knob, in an in-between position, instead of the coolest setting.

I also had used an Esteem several years ago and had to replace the thermostat one summer, when the AC started blowing hot air. So a thermostat does do its intended job, according to me.
Bomi
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Old 18th April 2007, 13:11   #9
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Yeah.. the compressor runs longer and hence mileage drops if temp control knob is not in full-cold position. The thermistor cuts off AC only when it is too cold for the compressor's working, and by keeping the temp-control knob in any position other than coldest we are mixing hot air ... making the compressor work longer.
I keep the temp control knob at full cold and control the cabin temperature by changing blower speed. It seems to work. My compressor gets cut off more frequently if I keep blower speed minimum.
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Old 18th April 2007, 13:22   #10
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I dont know if its related but On the highway I kept the temp control at 3 nicks less max. Looked as if it gave good mileage. But on the other hand it fell in the city. Any connection with this?

I changed the temp control for the first time then.
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Old 18th April 2007, 16:12   #11
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esteem lover,
went through the whole post. this is what elf said-
Default A/c Compressors...
Here's a pic of a typical simple HVAC (Heating / Ventilation / Air-Conditioning) Console.



THE CONTROLS.

*
The blower speed regulator sets the speed of the fan that blows the air into the vehicle cabin.
.
*
The air conditioning button puts the compressor on & off manually.
.
*
The vent selector allows you to select the vents through which the blower will blow the air. The pre-sets are through :
1. the floor vents only;
2. floor & dashboard vents;
3. dashboard vents only;
4. the dashboard & the front windscreen vents;
5. front windscreen vents only.
.
*
The temperature control knob allows you to set the ratio of hot or cold air, or a permutation of both that you want through your cabin.
.
*
The fresh air / recirculated air selector (not labelled above) lets you choose between recirculating the air already in your cabin, or opening a flap (often on your firewall) to let in air from outside your cabin.

HOW IT WORKS after you've been driving for some time.
Firstly, your compressor comes on when both your blower speed is on the first setting & your air conditioning button is on. Without these two in that state, the a/c compressor is off. I guess most of you know this bit.

You can set the volume of air, as well as it's relative temperature & the position from which it blows using the controls above. You also have a choice of fresh air if desired.

On the first blower setting with the a/c switch on, the air in recirculated mode & the temperature conrol knob on cold (most relevant in hot parts of India, which is pretty much everywhere!) your compressor cycles between off & on pretty often, as the a/c presumes you'd like to keep it cool but not cold. This is also the most economical mode of driving with the a/c on.

Level two on the blower increases the fan speed & also cycles the compressor less, with it going off less often.

Level three puts off your compressor even less than that, & only when it's close to freezing.

Level four simply leaves the compressor on (at least I've never seen it go off) & chills your cabin till your teeth rattle & you have sweat icicles forming off the front of your eyebrows. Polar bears are most comfortable at this setting, though some of them have been known to complain (there's no pleasing some animals!).

There is also a sensor on your throttle (sometimes below the accelerator pedal) that figures out when you want more power from your vehicle (like during overtaking manoeuvres) & cycles the compressor off. This of course, was unless you had a Premier 118 NE, which used to do it arse-backwards, by turning on the compressor when you accelerated, & turning it off when you were standing still & idling in traffic.

Anyways, enough typing. Somebody else should now explain further...
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this is what supreme baleno said-
Originally Posted by Floyd de Souza
Does fuel consumption increase as you shift the temp control to the right i.e. towards the red zone? A mechanic (supposed to be good with car AC's) told me that fuel consumption will increase as more hot air gets mixed with the cold air from the AC and hence the AC has to work harder and this has a negative effect on fuel consumption. He suggested that the knob should be at the coolest point and the AC should be switched on and off to maintain the desired temperature. In my Baleno. I feel that the compressor cuts off earlier as the knob is moved towards the red zone.
Well, MUL says the same thing as your mechanic - keeping the temp control at any setting other than the extreme cold will result in warm air mixing with cold air.

Evening drives have been an issue for me because even with the blower at lowest speed, it gets damn cold in the Baleno. So initially I used to do what your mechanic said, switch off the A/c when it gets too cold. But then, the drawbacks are getting distracted from driving due to frequently having to switch on and off the a/c and possible damage to the switch due to too much usage. Currently what I do is move the temp control to the right, till almost the centre where the cold range starts. This keeps the inside temp at a reasonable level and I am quite satisfied.

However, I am not sure about the effect on FE due to this practice. I do not think it will reduce the FE (as I also see frequent compressor cut-offs in this mode), but don't have any stats to prove the point.
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Last edited by supremeBaleno : 5th February 2007 at 12:37.

so i think my point is true.atleast i was fooled into beliving that compressor will be straining less when a warmer temperature is selected.
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Old 18th April 2007, 16:27   #12
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Quote:
Originally Posted by Bomi View Post
Perhaps your lever is not doing what it is intended to do. In my 7 year old Zen, I can hear the compressor cut out, with a distinct click. And it cuts out sooner, if I keep the thermostat knob, in an in-between position, instead of the coolest setting.

I agree even in My Alto it seems to work although no click sound. But the comprssor do swtich off more frequently & there is a slight diff in mileage too
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Old 18th April 2007, 20:16   #13
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Ok Here is my two cents....
We don’t get cool air (not only) because of compressor we get it because the air comes from a cooling coil that is cold enough to cool the air that passes through it. If there will be any other way to cool that coil we will still get cool air.
So the most important component that can be regulated to control temperature is the cooling coil (which is usually located under the dashboard in most cars). When hot air passes through the cooling coil (you can term it as a heat exchange)…the air temperature gets reduced and the cooling coil temperature gets increased. The compressor works constantly to keep the cooling coil at a predefined temp which when achieved will cut off and restart after a gap of 2-3 degrees. How fast will the cooling coil loose its low temperature will depend upon blower speed, compressor capacity and the temperature of the hot air that needs to be cooled. Assuming same capacity compressor and same temperature of hot air…. the speed at which the air is passed through will directly affect the cooling coil temperature. The speed of air that passes through the cooling coil is regulated by the blower knob. So if the speed is less the cooling coil will reach the optimum temperature more quickly, this will lead compressor to cutoff. If the blower speed is high it will take longer for the cooling coil to reach that optimum temperature to cut off the compressor. It’s always advisable to use lower blower speed so that the cooling coil reaches the optimum temp. faster to cut the compressor (increase in FE). The other reason for use of low speed blower is that it will also reduce the frequency of cleaning the air filter of A/C (because less air it passes through less will be dust sucked in)

Thanks,
Rohit
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Old 18th April 2007, 21:08   #14
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Well i think your probably right on this one rohit...and to increase Fe while driving..it is needed to put the a/c switch on and off from time to time depending on how fast the optimum cabin temp is reached...Wht i do is that when i start driving i start the blower on 2 with the a/c on...reduce the blower level to 1 with the a/c switch on..then after i know its getting a bit chilly..i switch off the a/c leaving the blower on..on 1...and switch it on when just before it starts to get uncomfortable...yes there is a lot of fidiling with the switch but it works for FE.
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Old 18th April 2007, 21:20   #15
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Well thats the best way. But we should also be careful that after we switch the a/c off we should not switch it on for atleast 2-3 minutes. It will do more harm than good!
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