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Old 19th April 2010, 16:08   #16
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Originally Posted by sanjayc View Post
Does the observations made in 2004 above still hold true with newer generation cars with new technology?

A few google searches seems to suggest that running a/c while idling is okay provided the temperature guage is within limits.

So asking again..is it ok to run the a/c while idling, and at the same time, working on a laptop connected to 12V socket (have done a couple of times on highways) for around 30 mins or so? FE apart, will it reduce engine/battery life to a significant extent?
The battery will definitely be under load definitely as the alternator will not be able to charge the battery efficiently as the connected load (AC blower, laptop charger, cabin lights, radiator fan) will consume more power than then alternator can provide.Hope this answers.
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Old 19th April 2010, 16:17   #17
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Originally Posted by Sheel View Post
It isn't recommended to i-d-l-e a motorcycle

^^ talking about extended period of around 1 hr+
Because a typical single cylinder small capacity engine like the ones have on the bikes here in India are air cooled, the engine if left to idle for too long may heat up too much and get damaged as it relies on the air passing through the fins when the bike moves.

The Cars on the other side has a liquid cooled engine with separate radiators with fan/s to keep it cool even when stationary.

Its absolutely all right to use a Car A/C when idling, the only issue is wastage of fuel and thereby damage to the environment.
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Old 19th April 2010, 16:18   #18
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Originally Posted by tj123 View Post
The battery will definitely be under load definitely as the alternator will not be able to charge the battery efficiently as the connected load (AC blower, laptop charger, cabin lights, radiator fan) will consume more power than then alternator can provide.Hope this answers.
From a layman's perspective, does that mean the life of battery will reduce? Significantly or marginally, if such usage conditions are only once in a while?. The reason I am asking this is since battery can be replaced relatively cheaply. Whereas, if such usage damages the engines, then maybe, I need to be more judicious regarding such usages.

Specifically, I am using Fiesta 1.6 Sxi Pertol, if that makes any difference (i.e., does a 1.6 engine will provide more electric power than a 1.2/1.3 one?) How do I find out how much maximum load I can put thru the 12V power socket?
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Old 19th April 2010, 16:22   #19
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Read through this tread, it was quite useful.

An ignorant question - I was under the impression that using A/C (manual) with a fan speed set to lowest (say #1) will be of minimal load to the engine. But a Maruti service engineer said that engine load for A/C does not depend on the fan speed (i.e fan speed #4 will have the same load as #1). Is this true? Thanks!
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Old 19th April 2010, 17:03   #20
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Originally Posted by sanjayc View Post
From a layman's perspective, does that mean the life of battery will reduce? Significantly or marginally, if such usage conditions are only once in a while?. The reason I am asking this is since battery can be replaced relatively cheaply. Whereas, if such usage damages the engines, then maybe, I need to be more judicious regarding such usages.

Specifically, I am using Fiesta 1.6 Sxi Pertol, if that makes any difference (i.e., does a 1.6 engine will provide more electric power than a 1.2/1.3 one?) How do I find out how much maximum load I can put thru the 12V power socket?
Once in a while usage won't impact the battery and it will charge up, but frequently "idle only" usage may significantly reduce battery life. All battery tends to wears down with usage (charging / discharging) cycles, also high/low temperatures adversely affects battery performance.

I think all the Fiesta petrol version alternators might be same, not sure ,need to check.

Not sure about the Ampere loads about Fiesta , easy way is to check for is the fuse rating, if the rating is 20 Amps(example) then you can use the Ohm's law to compute the safe wattage rating
Wattage= Volt (12) * Current (20) = 240 Watts load ( safe usage will be around 85% of the rated output = 200 W approx.)
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Old 19th April 2010, 17:35   #21
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Originally Posted by mTorque View Post
I was under the impression that using A/C (manual) with a fan speed set to lowest (say #1) will be of minimal load to the engine. But a Maruti service engineer said that engine load for A/C does not depend on the fan speed (i.e fan speed #4 will have the same load as #1). Is this true? Thanks!
A typical car compressor has only two modes either ON or OFF. No matter what speed the blower is set to the compressor will the same load on the engine.

There are some exceptions like the Mahindra Scorpio where compressor can be run on HI or LO depending on the requirement.


Quote:
Originally Posted by sanjayc View Post

Specifically, I am using Fiesta 1.6 Sxi Pertol, if that makes any difference (i.e., does a 1.6 engine will provide more electric power than a 1.2/1.3 one?) How do I find out how much maximum load I can put thru the 12V power socket?
The Power socket outlet in my Elantra has '100W MAX' mentioned

Last edited by .anshuman : 19th April 2010 at 17:37.
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Old 19th April 2010, 17:51   #22
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Thanks tj/anshuman..your inputs helped a lot. Seems like you are the only experts, at least regarding a/c out here Surprising that in this summer heat, a thread like this is missing attention for others!

Taking the discussion a little further, to get the maximum out of the a/c (or more appropriately, to keep the a/c performance at its optimum), what is that we can do on our own AND what is strictly to be done at dealer end? Is there any regular preventive maitenance that needs to be done?
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Old 19th April 2010, 18:04   #23
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Originally Posted by sanjayc View Post
To get the maximum out of the a/c (or more appropriately, to keep the a/c performance at its optimum), what is that we can do on our own AND what is strictly to be done at dealer end? Is there any regular preventive maitenance that needs to be done?
Most newer cars come with Pollen filter in the AC, the filter needs to be cleaned/changed at manufacturer specified intervals, the interval is mentioned in the owner's manual. For Example: The Punto's Pollen filter should be changed at every 15k kms service whereas The one in Elantra should be checked and cleaned(replace if required) at 20k kms. The AC filter for Punto costs ~250 bucks whereas the one for Elantra costs around 2k.

After the introduction of Pollen filters the AC system does not need to be serviced every year like before, I never had to get the Elantra's AC serviced ever. The car has done 130k kms since 2006, i got the AC checked recently its in perfect condition, the gas and oil were changed when the AC coil was changed.

At every Service ask the Service advisor to check the AC gas and oil levels, using the AC with inadequate Gas or Oil might damage the AC system and will reduce the cooling efficiency.
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Old 19th April 2010, 18:17   #24
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Quote:
Originally Posted by mTorque View Post
I was under the impression that using A/C (manual) with a fan speed set to lowest (say #1) will be of minimal load to the engine. But a Maruti service engineer said that engine load for A/C does not depend on the fan speed (i.e fan speed #4 will have the same load as #1). Is this true? Thanks!
Instead of keeping the temperature setting (thermostat setting) at 20 deg and fan blower at 2, it is always better to keep temperature at 24-25 deg and fan blower at 4-5. This way you'll make sure that the compressor does not turn ON and OFF very often and you'll save quite some fuel with a very negligible drop (if any) in comfort level of cabin.
Whenever i feel the car cabin has cooled enough, i just increase temperature setting by one or two degrees instead of reducing the blower speed. Helps save fuel as the compressor will be OFF for more time.
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Old 19th April 2010, 18:47   #25
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@.anshuman, @Akki_5 - Thank you!
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Old 19th April 2010, 21:25   #26
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Quote:
Originally Posted by .anshuman View Post
Most newer cars come with Pollen filter in the AC, the filter needs to be cleaned/changed at manufacturer specified intervals, the interval is mentioned in the owner's manual. For Example: The Punto's Pollen filter should be changed at every 15k kms service whereas The one in Elantra should be checked and cleaned(replace if required) at 20k kms. The AC filter for Punto costs ~250 bucks whereas the one for Elantra costs around 2k.

After the introduction of Pollen filters the AC system does not need to be serviced every year like before, I never had to get the Elantra's AC serviced ever. The car has done 130k kms since 2006, i got the AC checked recently its in perfect condition, the gas and oil were changed when the AC coil was changed.

At every Service ask the Service advisor to check the AC gas and oil levels, using the AC with inadequate Gas or Oil might damage the AC system and will reduce the cooling efficiency.
That's great..thanks for the info....kudos to car-makers for coming out with idiots-like-me proof solutions.
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Old 19th April 2010, 21:46   #27
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Quote:
Originally Posted by Sheel View Post
Does idling hamper the engine in any way?
anyone

Quote:
Both Diesels as well as Petrols
Any difference guys?
can diesels be idled more than petrol or such?

Quote:
^^ talking about extended period of around 1 hr+
Not initial idling, but with AC ON and for more than an hour in sun
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Old 19th April 2010, 22:16   #28
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Quote:
Originally Posted by sanjayc View Post
is it ok to run the a/c while idling, and at the same time, working on a laptop connected to 12V socket (have done a couple of times on highways) for around 30 mins or so?
Issues when running the car on idle, with aircon on:
  • At idling rpm, most alternators manage to generate around 2-3 amps (for low rpm operations, a smaller alternator pulley can increase alt rpm, generating higher current - used to do this in CCU where traffic used to crawl and the battery went dead due to frequent stop-starts as a fuel-saving exercise);
  • The current requirement to keep the engine, aircon and other systems running is around 8-10 amps;
  • So effectively the battery discharges @ around 5-8 amps - for a, say, 80Ah fully charged battery, this should be theoretically doable for 8-10 hours before you have a totally flat battery;
  • OTOH, the water pump is turning over at a sub-optimal rpm;
  • This allows for inadequate heat dissipation from an engine that is already partially loaded with the work of running the aircon compressor;
  • In peak summers this has a potential to cause overheating;
  • The oil pump is also running at sub-optimal speeds;
  • As a result the top end of the engine potentially may not get adequate lubrication, leading to increased wear of valves & guides, cams, rockers etc.
  • There is not enough exhaust flow at idle to wash out the gases from the catcon, silencer and exhaust manifold;
  • The exhaust system runs superheated after a while, with soot accumulation happening esp. if it's a diesel (this also can set off a fire under your car if you are parked on dry grass);
  • This will likely lead to reduction in catcon efficiency, and possibly its total ruin.
To summarize, running the car for 30 minutes as you describe is not going to cause any significant harm to either engine or battery (or any other component), but running it that way for 3 hours would.

Hope this helps.

Last edited by SS-Traveller : 19th April 2010 at 22:21.
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Old 19th April 2010, 22:25   #29
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SS Da, thanks for the extensive explanation. So in a nutshell, while keeping one eye on the watch, another eye should be at the temp guage. As long as the engine temp is hovering around normal, we should be able to wrap up some unavoidable work in a/c comfort.
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Old 19th April 2010, 22:45   #30
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Quote:
Originally Posted by SS-Traveller View Post
Issues when running the car on idle, with aircon on:
  • As a result the top end of the engine potentially may not get adequate lubrication, leading to increased wear of valves & guides, cams, rockers etc.
  • There is not enough exhaust flow at idle to wash out the gases from the catcon, silencer and exhaust manifold;
  • The exhaust system runs superheated after a while, with soot accumulation happening esp. if it's a diesel (this also can set off a fire under your car if you are parked on dry grass);
  • This will likely lead to reduction in catcon efficiency, and possibly its total ruin.
To summarize, running the car for 30 minutes as you describe is not going to cause any significant harm to either engine or battery (or any other component), but running it that way for 3 hours would.

Hope this helps.
Agree with the topend lubrication problem. Lubrication of overhead cams is always a problem, esp. during starting and idling. A particular series of engines (of one of the big three) was famed as a cameater. Maybe to overcome perception, they introduced the Rocam

However, why should the catcon get ruined. Agreed it will be way below "light-off", and thus not working, but ruined?

Regards
Sutripta
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