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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 26th September 2006, 08:14   #76
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Quote:
Originally Posted by adya33
How much load the AC puts on engine?
What if you are starting off your journey with 4 passengers and some luggage (w/o switching on AC), in such case you will be putting more load on engine.
Hi,

An AC puts anything between 8% to 17% load on an engine depending on the size of the engine, type(diesel/petrol) compressor etc irrespective whether you start when cold or hot.

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Old 26th September 2006, 11:57   #77
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i dont think it makes a difference when u turn on AC on cold / hot start.

Ive been starting the engine and say within next 10 seconds the AC is ON, been doing this for last 4 years and dont see any way the engine is getting weak and the weekly run was approx 1400 kms (abu dhabi dubai daily) with 100% AC usage.

Logically ur reasonings hold good but the above is my personal experience.
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Old 26th September 2006, 21:05   #78
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I don't know the technical reason but once i was advised to start the blower first and let it run for sometime say a minute then switch on the AC ...
i have been practicing such way since i heard this...

maybe just like people letting their engine run atleast for half a minute after start before flying off ... i guess
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Old 26th September 2006, 21:26   #79
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Well the practice of opening rear window seats might be good! however people who do not have power windows need to sweat out bringing the glass down and up if they are driving alone.

However, I switch on the AC after 5-10 mins of drive or some times I do not switch on. Just the blower on. Bangalore is pretty cool early in the morning and hence switching AC after starting may be ruled out!
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Old 27th September 2006, 14:03   #80
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Quote:
Originally Posted by rranjith_kum
I don't know the technical reason but once i was advised to start the blower first and let it run for sometime say a minute then switch on the AC ...
i have been practicing such way since i heard this...

maybe just like people letting their engine run atleast for half a minute after start before flying off ... i guess
that was a good advice someone gave you. by switching on the blower for a minute, you are letting your engine heat up & at the same time you will not be sweating very badly.
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Old 27th September 2006, 20:18   #81
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It is the same concept as provided for the home window Acs. Switch on the fan for a minute or two and then kick in the compressor. And shut down the same way - cut off the compressor and let the fan run in for 1 or 2 minutes.

I too have been following the same for ages alongwith driving the vehicle for a Km or so and then adopting this procedure. My vehicles have nere given me any trouble over this ever..!!

Quote:
Originally Posted by rranjith_kum
I don't know the technical reason but once i was advised to start the blower first and let it run for sometime say a minute then switch on the AC ...
i have been practicing such way since i heard this...

maybe just like people letting their engine run atleast for half a minute after start before flying off ... i guess
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Old 27th September 2006, 21:30   #82
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Quote:
Originally Posted by gd1418
It is the same concept as provided for the home window Acs.
Don't confuse this concept with the one followed for home ACs. it is completely different.
In home ACs you just have to wait 2+mins before RESTARTING the compressor, and that is b'coz for some concept of gas needing to settle down otherwise there is too much load on the compressor to start and it even might fail to start.

Car ACs are too small to be affected by this funda and they run on mechanical power so its all very different. (i.e. the engine has much more power available to restart the AC under any circumstances)

So what we are talking about here is a bit different i.e. load of the AC on the cold engine. Also its not just the AC but one shouldn't even be driving an extremely cold engine.

Last edited by SLK : 27th September 2006 at 21:36.
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Old 28th September 2006, 01:23   #83
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Quote:
Originally Posted by adya33
How much load the AC puts on engine?
What if you are starting off your journey with 4 passengers and some luggage (w/o switching on AC), in such case you will be putting more load on engine.
I kinda agree. i guess you shud wait in that case until the engine is warmed up well. especilly if starting at low temperatures.
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Old 28th September 2006, 08:28   #84
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Default Home AC concept

SLK: My statement was not meant to confuse the concept. What I was primarily stating was that what the person was following was a typical home AC concept.

If you read my earlier posts on this subject, I've outlined as to what I practice while switiching on AC ona cold engine or the first thing in the morning.

Bests,

Quote:
Originally Posted by SLK
Don't confuse this concept with the one followed for home ACs. it is completely different.
In home ACs you just have to wait 2+mins before RESTARTING the compressor, and that is b'coz for some concept of gas needing to settle down otherwise there is too much load on the compressor to start and it even might fail to start.

Car ACs are too small to be affected by this funda and they run on mechanical power so its all very different. (i.e. the engine has much more power available to restart the AC under any circumstances)

So what we are talking about here is a bit different i.e. load of the AC on the cold engine. Also its not just the AC but one shouldn't even be driving an extremely cold engine.
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Old 5th February 2007, 13:20   #85
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Quote:
Originally Posted by esteem_lover View Post
by switching on the blower for a minute, you are letting your engine heat up & at the same time you will not be sweating very badly.
Hey EL , I did not get the bold part of your post ? How can the blower help to get the engine heated up ? As far as my limited knowledge goes , the blower has absolutely no role in the engine heating up ? Anyone here who can explain
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Old 5th February 2007, 13:26   #86
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Default Temperature control knob

AC experts...can you please clear my confusion by answering this question.

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.

Your take on this please.

Sorry for the double post as I thought the earlier one had'nt registered. Mods please delete the earlier post.

Last edited by Floyd de Souza : 5th February 2007 at 13:28.
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Old 5th February 2007, 13:36   #87
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Quote:
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.

Last edited by supremeBaleno : 5th February 2007 at 13:37.
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Old 5th February 2007, 14:05   #88
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Thanks SB...I too do the same as you i.e. keep the TC knob in the white area just before the red zone but that mechanic claimed that FE could drop by around 0.5kmpl by doing this. 0.1 or 0.2 kmpl difference can be digested but a 0.5kmpl difference is difficult to ignore.
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Old 5th February 2007, 14:25   #89
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Quote:
Originally Posted by normally_crazy View Post
Hey EL , I did not get the bold part of your post ? How can the blower help to get the engine heated up ? As far as my limited knowledge goes , the blower has absolutely no role in the engine heating up ? Anyone here who can explain
The engine cannot get heated up by switching on the blower. What i meant was, when you idle the engine in the mornings while sitting in the car without the AC (which is the best option), if the blower is on, then at least that helps prevent too much sweating.
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Old 5th February 2007, 15:16   #90
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Hi. The blower is always on in the cars, either setting 1 or 2. But before turning the engine off, the compressor is turned off and few seconds is waited for the engine to release the load. Then it is turned off.

While starting, the blower is still on, but the compressor is turned on only after a minute or two, or atleast when the car's temperature gauge comes out of the cold zone, because the cars consume lots of fuel when the car is getting heated up and along with the a/c running.
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