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View Poll Results: How long do you wait to switch on the AC in your car during a cold start ?
Immediately on starting 52 22.51%
1-2 Mins after start 92 39.83%
4-5 Mins after start 71 30.74%
10 or more Mins after start 16 6.93%
Voters: 231. You may not vote on this poll

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Old 7th February 2007, 11:15   #106
k36
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Default What's the actual use of the thermostat?

In Swift, I have never observed the compressor getting cut off. A maruti service engineer explained that the thermostat will cut off the compressor only at very low temperatures, to prevent freezing. Its not meant to regulate the cabin temperature. Cabin temperature is regulated only by mixing hot and cold air.. with the compressor running continuously.
The explanation seems to match with my experience (compressor never getting cut off). But isn't this a drain on fuel consumption?
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Old 7th February 2007, 12:04   #107
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ok let me give it a try -

In the vRS climate control aircon system , I have the temperature set to 18 , now after some time , say for example 45 minutes , the compressor cuts off "tak-tak" is noise - according to the very little understanding I have this happens because the sensor senses that the cabin temperature has reached the set value and it cuts the compressor off. After a while when it starts to get warmer again in the cabin, the compressor gets to work.

Similarly if inbetween I increase the set temperature value from 18 to 20 , instantly the compressor is cut off. Similar thing happens in non-climate control ac systems , when you move the knob to nuetral the compressor cuts off because temperauture of air coming from the ac is almost the same as the temperature in the cabin. Its only when you shift the knob to the heater / red zone , the heater is activated and you feel the hot air.

So if you have set the ac knob in the white zone , I feel its the same as driving with the ac off (Feel free to flame me and correct me if Im wrong) and should not have any adverse effect on the FE.

As far the other question is concerned - switching on the ac immediately after starting the car - the only reason I dont so it is because the engine has to work extra hard in the initial phase after cold start up ( the oils and stuff are thick ). So after I see the temperature indicator rise to a 30 degree angle , I feel mentally satisfied that the engine and its oils and its parts are well lubricated and working "SLICKLY" and can take load much easier - I switch the ac on.

Just to give an example - how many of you can start working / reading / brushing immediately after you wake in the morning ? You take some time , rub your eyes , stretch yourself , swing your legs off the bed , compose yourself , wear your slippers , walk slowly to the bathroom and wash your face which helps right ? After washing you are able to things better right ? Well atleast I do

Similarly for our babies, thats what I think.

Last edited by normally_crazy : 7th February 2007 at 12:05.
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Old 7th February 2007, 16:33   #108
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Quote:
Originally Posted by k36 View Post
That's not the case, please try the following: While keeping the AC OFF (manually) adjust the temp-control knob within the cold-neutral range. You will notice the change in air temperature as you move from cold towards neutral. What, other that hot air mixing, can cause this?
agreed. i guess that's the difference "climate control" makes.

Last edited by vivekiny2k : 7th February 2007 at 16:38. Reason: just used the search function to verify.
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Old 7th February 2007, 21:32   #109
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Quote:
Originally Posted by k36 View Post
That's not the case, please try the following: While keeping the AC OFF (manually) adjust the temp-control knob within the cold-neutral range. You will notice the change in air temperature as you move from cold towards neutral. What, other that hot air mixing, can cause this?
I think when the ac is off , the only air that flows into the cabin is the outside air. this happens in all cars with or without climate control systems. When the ac is off i havent noticed a change in temperture of the air flowing in - neither in the ikon nor in the cimatronic system of the vRS.
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Old 7th February 2007, 21:49   #110
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i think you could be wrong there n_c. immaterial of whether the ac is on or off, the air intake control in the dash controls which air is circulated inside the cabin. the second part is right. when the ac is off, there is no change in the temp of air from the vents until a little while after the chillness inside the cabin drops.

i agree there is no control over the thermostat by sliding the cold/hot switch.
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Old 22nd April 2007, 00:47   #111
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Default seems like more

Quote:
Originally Posted by tsk1979 View Post
Well if you start moving the car it is going to put much more load.
When we talk about not running the car at high rpm for first few minutes it means do not utilize full power initially.
With 3bhp increase we are still nowhere close to utilizing full power.
By this logic cars should idle for 5 minutes before even starting off, because when we go to 1500rpm its like 20-30hp more from the engine!
I made an observation about loading caused by AC. After the engine settles down at idle RPM say 650, I switched on the AC and found it causes an RPM increase of 50 with fan at level 2. Can I say the load exerted is about 7% more at idle RPM ? The car is a Petra 1.6.
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Old 22nd April 2007, 00:58   #112
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not really, its the rpm advance function happening, this is inbuilt in all oe ac equipped cars so as not to stall the car when starting off (motion)

ecu cars do it electronically, carb cars do it using vacum actuators in the carb
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Old 22nd April 2007, 12:00   #113
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Just a question: Is it possible to set the engine speed (RPM) in a car with an ECU?

For example, set the idle RPM at 700RPM without the a/c, & 900 with it.
If so, how?
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Old 22nd April 2007, 16:39   #114
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yup I think it is. It happened in my alto I can feel it idle higher after the service.

Also after this times lancer service the idle rpm has gone up at cold to 1600-1800rpm. then it settles back to 800rpm.
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Old 2nd July 2007, 02:47   #115
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Default Switching on Your AC in Cold Start

I mostly use the AC whenever I use my car and I was told by the service center to turn on the blower first and then turn on the AC.Usually I pull up all the window glasses then turn on the blower for about 2-3 minutes in full blast and then turn on the AC.Is this the correct procedure to follow.Again,I the car sits idle for about 2-3 days in the week.Is it necessary to "idle" the car before each use or should I drive for aleast a few kms before switching on the AC?
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Old 2nd July 2007, 06:20   #116
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You should start the blower first and blow out all the hot air with the windows rolled down for a few minutes before switching ON the AC if the car has been parked for a while in hot weather.

It's always advisable to run the engine in idle for a minute during the 1st start of the day irrespective of how old the car is.
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Old 2nd July 2007, 09:10   #117
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It is a good practice to leave the car in idle mode every morning for a minute or two before taking off. I usually turn on the AC after the car has travelled a few hundred meters. I don't know why I do this, but I do. I also switch off the AC at red lights.
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Old 2nd July 2007, 09:19   #118
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Quote:
Originally Posted by mithun View Post
It's always advisable to run the engine in idle for a minute during the 1st start of the day irrespective of how old the car is.
I want to know why this is advisable. Any specific reason for this?
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Old 2nd July 2007, 14:37   #119
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Quote:
Originally Posted by Sudipto-S-Team View Post
It is a good practice to leave the car in idle mode every morning for a minute or two before taking off. I usually turn on the AC after the car has travelled a few hundred meters. I don't know why I do this, but I do. I also switch off the AC at red lights.
even I have this habit of turning on the AC after I have crossed a few blocks from my house - usually its easier for me to negotiate the local traffic in the congested part near my house with the windows rolled down...and even I turn of the AC at RED signals as I usually turn off the start
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Old 2nd July 2007, 14:47   #120
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this thread could be of help.

http://www.team-bhp.com/forum/techni...d-start-8.html
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