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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 20th September 2006, 23:32   #31
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I never shut off my ac. So the car starts with it only.
The only care I take in case of a cold start is not to push the car.

But I'm wondering does it harm the engine or the battery??
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Old 21st September 2006, 01:31   #32
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Quote:
Originally Posted by Fuelled
I never shut off my ac. So the car starts with it only.
The only care I take in case of a cold start is not to push the car.

But I'm wondering does it harm the engine or the battery??

yea it puts a lot of load on the battery.which in turn will reduce your battery life.


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Old 21st September 2006, 02:42   #33
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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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Old 21st September 2006, 04:26   #34
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Quote:
Originally Posted by nitrous
@esteem_lover: No matter how enthusiastic u're about cars, when u live in a place like chennai, u just switch on the AC as soon as the ignition is turned on.
All the blah-blah about engine condition,AC condition isn't much cared for.
Moreover, Synthetic oil always helps keep the engine from wear&tear!
I second that.Chennai is simply toooo hot and some times during power cut(lot of time ) We just roam in car for some time just to enjoy the A/C.
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Old 21st September 2006, 06:49   #35
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I normally do not shut off the A/c. This is because, in Chennai, even in the mornings, we will feel the heat and humidity (atleast I get a lot sweat). I never thought of that this could cause load on battery. I will change this practice.
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Old 21st September 2006, 08:54   #36
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Default Starting with AC on

It puts a hell of load on the battery and the ampereage drops drastically while cranking. This results in the cells getting weak and one of these days without warning the battery will die on you.

As far as the engine is concerned, during first start an idle for 30-40 secs is must for the oil to circulate and lubricate all moving parts. With the ac on the it puts a starian on the engine and the wear & tear would be higher.

Quote:
Originally Posted by Fuelled
I never shut off my ac. So the car starts with it only.
The only care I take in case of a cold start is not to push the car.

But I'm wondering does it harm the engine or the battery??
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Old 21st September 2006, 11:43   #37
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elf, that was a detailed and informative article.

Quote:
Originally Posted by elf
On the first blower setting with the a/c switch on, the air in recirculated mode & the temperature conrol knob on cold your compressor cycles between off & on pretty often. This is also the most economical mode of driving with the a/c on.
This is my understanding too and what was suggested by the MUL engineer (in a response to my query) as the way to go to get most FE when using a/c.

This works pretty fine for me during the day as the Baleno a/c does a neat job at the lowest fan setting, even in Chennai. The problem comes in the evenings/night when I drive back home. Even this lowest fan setting becomes just a little too cold for comfort. I tried moving the temp. control knob from "cold" position to the centre so as to reduce the cooling a bit, but did not seem to make much of a difference.
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Old 21st September 2006, 12:03   #38
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Quote:
Originally Posted by magiceye
The opening/shutting of the rear windows theory is possible if you have power windows otherwise you will be drenched in sweat by the time you go thru this procedure! .
I agree....will be a tiresome activity in rush hour..
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Old 21st September 2006, 12:24   #39
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Quote:
Originally Posted by supremeBaleno
elf, that was a detailed and informative article.

This is my understanding too and what was suggested by the MUL engineer (in a response to my query) as the way to go to get most FE when using a/c.

This works pretty fine for me during the day as the Baleno a/c does a neat job at the lowest fan setting, even in Chennai. The problem comes in the evenings/night when I drive back home. Even this lowest fan setting becomes just a little too cold for comfort. I tried moving the temp. control knob from "cold" position to the centre so as to reduce the cooling a bit, but did not seem to make much of a difference.
i second supremebaleno on that. the hot cold slider does not decrease the cooling in any way. it is there just to switch between cold & hot. hope someone who knows about these things can throw some light on this, please.
cheers
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Old 21st September 2006, 12:48   #40
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You guys with the non-working hot air settings should get your heater circuits checked. It may be something as simple as blown / unreplaced fuses.

Sometimes, local a/c chaps simply disconnect the heater systems - something which was brought to my notice by Israr Khan (Israrbhai), one of the best a/c guys in Bombay (tel: 022-26412094). He said that the entire heating system is often cancelled by most local 'repair' chappies when it stops functioning due to disuse, & it's a pain to get working again.

He's a bit expensive, but definitely definitely knows his way around air conditioning systems. The other alternative I know would be your authorised service centres.
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Old 21st September 2006, 13:22   #41
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Quote:
Originally Posted by Fuelled
I never shut off my ac. So the car starts with it only.
The only care I take in case of a cold start is not to push the car.

But I'm wondering does it harm the engine or the battery??
Neither. If you notice carefully, all other loads (A/C, audio, lights) are switched off momentarily at the time of cranking. This is true of the Indica - I'm not too sure about other cars.

Last edited by hrag : 21st September 2006 at 13:25.
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Old 21st September 2006, 13:41   #42
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@hrag: This holds true for Alto too & I believe rest of the MUL cars as well

Elf: Thanks for letting people know because I have been effectively using teh cold-hot lever to adjust cooling temperature in car since long & nobody believes me :(
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Old 21st September 2006, 13:56   #43
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@hrag: You're right. All electricals go off when the car is cranked, to optimize the juice sent to the starter motor.

This temporarily knocks off your a/c as well. However, for older batteries, the alternator now needs to pump a bit more juice into the battery to bring it back to speed, which is why it's one more reason to hang on for a bit before thwacking your a/c on. Guys with big ICE demands also note.
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Old 21st September 2006, 15:19   #44
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Quote:
Originally Posted by elf
@hrag: You're right. All electricals go off when the car is cranked, to optimize the juice sent to the starter motor.

This temporarily knocks off your a/c as well. However, for older batteries, the alternator now needs to pump a bit more juice into the battery to bring it back to speed, which is why it's one more reason to hang on for a bit before thwacking your a/c on. Guys with big ICE demands also note.
cranking the engine with the AC set on is a definite no no, even if you think that all electricals are knocked off at that moment. the reason why all electricals are knocked off is because the crank requires the full battery energy, not for any other reason. in fact, in my car, there have been many times when my ICE was on & never shut off when i cranked the engine. that was when the battery was at its best, fully charged. please try switching on your lights & starting your car to realise that only accessories are turned off in 'Certain' models of cars, certainly not in my 1998 esteem.
also, are you not straining your engine even before it settles on an even rpm ?

of course, there are certain cars, i think skoda has it, where the AC simply will not come on even if you had switched it on, until the engine settles down or warms up. that is a special feature, not standard.
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Old 21st September 2006, 15:35   #45
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el: even in my brand new Alto all the systems, except for the lights, go off when I crank the engine. May be its a new feature which is why you might not have seen it in your esteem :-)
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