[Shashank.A]

Originally Posted by Path_Finder

Very True - The difference is very much noticabe - with smaller cars switiching off the a/c is specificaly useful while overtaking to get that extra thrust.

With the AC on I was not able to push it beyond 120, but after I put it off, I was able to drag it to 138 on the fourth Gear itself.

And yes, its does feel like a rocket booster has been activated when you switch the AC off.

There is a feeling in the Esteem as well, but its not as noticeable as in Alto.

[Path_Finder]

Originally Posted by Shashank.A

With the AC on I was not able to push it beyond 120, but after I put it off, I was able to drag it to 138 on the fourth Gear itself.

And yes, its does feel like a rocket booster has been activated when you switch the AC off.

There is a feeling in the Esteem as well, but its not as noticeable as in Alto.

Folks, to clarify - my observation is more on M800, earlier Zen. I have not driven the Alto - so not sure how noticebale it is.

[vnabhi]

Originally Posted by Path_Finder

Coming to Nitin’s usage queries - I would recommend not doing the manual off/on very frequently. This is not good for compressor which is why your home a/c stabilizer usually has a 1 minute cut-off.
............. But it does make some difference in city driving – but do give at least 2 minute gap in between operating the switch.

I disagree with this bit, based on my experience.
I used to give a 2 min gap between switch on and switch off in my WagonR, until I saw a pal in an Accent switching it on and off in seconds, especially in 2nd gear to get a boost in pickup. I too started practising the same for the past 6 years on my WagonR, moreso to prevent autorickshaws from overtaking me when there is a gap in the bumper to bumper traffic. Touch wood, my AC is fine for the past 7 years, and i've not even changed the gas!
So to 2 or 3 minute rule applies only to home ACs, not car ACs.

[viper_711]

Originally Posted by cooldude1988765

I am sure any car equipped with an ac/heater will have a thermostat. The knob with the blue and red markings is the thermostat.

That is so not cool dude! (sorry, couldn't resist that!)
The knob you mention is not the thermostat. Please read the posts before your post and read the one by merve extreme a few post after your post.

[teknophobia]

On my car you can easily make out that the compressor is switching on and off, there is an audible click. In idle, the RPM drops and rises slightly as the compressor goes on and off.

[amu1983]

Good to know that there's no such thing as the 2 minute rule! Even I like using the AC button as the Nitro booster, especially when I badly need some power and don't want to strain the engine too much (with the AC and the acceleration). Even I was worried about the health of my compressor, and the ill effects of frequent ON/OFFs. Good to know about the 7 year-WagonR guy.

[akrish01]

My 2 cents worth. I own a Getz Prime 1.3 GLS purchased in April 2008. I have been fiddling around with the AC settings & trying to find out what difference it gives in my mileage. My observations are given below:

1) When the rotary knob (which I think is the thermostat) is fully towards the blue, in city traffic, I used to get around 9 - 10 kmpl. AC was used 90% of the time. I used to switch off the AC once in a while when I felt too cold.

2) I then moved the rotary knob half-way through (between the red & blue markings). I also inflated my tyres 10% more (instead of the recommended 30 psi, I inflated it to 33 psi). My mileage went up to 10 - 11 kmpl.

3) Now, I'm presently running without using the AC. I will know my exact mileage only when I tank up the next time, which should be sometime next week. But, I can tell for sure that my mileage has gone up by about 35%. I haven't checked my tyre pressure yet but it's definitely at least 30 psi.

All the above runs were fully city driving only.

My car is due for 2nd service in about a month's time. After service, I expect mileage to increase by 10 - 20%.

Krishnan

[akrish01]

More observations from me.

I feel that my mileage has gone up by at least about 30% when I drive without the AC as reported earlier. The main reason for this, I feel, is because I'm able to shift into higher gears (3rd gear onwards) quicker than when I'm driving with the AC on. I'm a very gentle driver - I accelerate & decelerate gently, using 2000 rpm as my guideline to shift from gear to gear.

On the highway, I think I was getting about 16 - 17 kmpl with the AC on - never tried it without the AC yet. I achieved this figure by not going over 80 kmph.

Krishnan

[cyclops]

Originally Posted by viper_711

Dude! Waiting for your observations!

hey viper.. sorry somehow missed this thread.
yes, my observation was as per your anticipation..

but i guess merve's post has made the concept clear for us.
the blue-red knob controls the thermostat as well as the hot air flow..

[Path_Finder]

Originally Posted by amu1983

Good to know that there's no such thing as the 2 minute rule! Even I like using the AC button as the Nitro booster, especially when I badly need some power and don't want to strain the engine too much (with the AC and the acceleration). Even I was worried about the health of my compressor, and the ill effects of frequent ON/OFFs. Good to know about the 7 year-WagonR guy.

I think I was the one who mentioned first about this 2 minute rule; that was based on how a typical home a/c is set to operate and its instructions. Good to see the experience shared here on the forum and that lower times do not really affect the performance or durability. It could also because that the modern units are built to last better.

I was observing the automatic cut-off happening on my CEDIA while idling after seeing this thread. Know what? While I was idling with a/c on I was observing that the compressor was getting automatic on & off every 40-45 seconds!! So that blows the myth off the 2 minute rule. So go after the “nitro booster” when you need it most.

[viper_711]

Originally Posted by cyclops

but i guess merve's post has made the concept clear for us.
the blue-red knob controls the thermostat as well as the hot air flow..

No dude! read his post carefully - he has said that the thermostat is fixed usually between 2 and 5 degrees and that the knob controls flow of hot coolant / air over the heater coil. You cannot control the temperature setting the way you can in a home window / split unit.
Hope it's clear now. cheers!

[cyclops]

Originally Posted by viper_711

No dude! read his post carefully - he has said that the thermostat is fixed usually between 2 and 5 degrees and that the knob controls flow of hot coolant / air over the heater coil. You cannot control the temperature setting the way you can in a home window / split unit.
Hope it's clear now. cheers!

yes man, as per him as well the thermostat is not controlled by the knob.

but i can definitely experience the frequent cut-off of the AC with the knob towards red as compared to completely towards blue

umm.. maybe i'm wrong, but I think it must be due to less air is being blown through the cooling coil when the knob is set more towards red.. as the flap will be directing more hot air in the mixture.. what say?

[viper_711]

Originally Posted by cyclops

but i can definitely experience the frequent cut-off of the AC with the knob towards red as compared to completely towards blue

umm.. maybe i'm wrong, but I think it must be due to less air is being blown through the cooling coil when the knob is set more towards red.. as the flap will be directing more hot air in the mixture.. what say?

Now that you're on this side of the fence - try and observe carefully for the next fifteen days - We have a palio sport 1.6 and an Indica TDI in the family. I too will try and observe what you say on both the cars (Hell, at most times in Bangalore weather one needs to tweak the temperature settings of the AC, especially on long commutes) Let's share views after that.

[jkdas]

How is the condenser and evaporator linked?

[mithun]

See this pic :



Courtesy : Air Conditioning, Page 1 of 3