[Mohnish]

Originally Posted by Dippy

....

Thanks you Dippy for an excellent and very helpful write up. I do have a query which possibly you could throw some light on:

My AC chap adviced me as follows with particular reference to my Benz and in general to all vehicles that have a heater/AC unit, as compared to vehicles that were not equipped with a heater unit (as in the old days) :

In cities like Mumbai (hot) when using the AC, always set the temp. to absolute cold ie. minimum temp. Do not set it midway, like 20degC or so, which is more comfortable for the occupants.

His reason: There is no thermostat to cut on/off the AC compressor to regulate temp. The temp is controlled by flaps that allow the hot / cold ait to pass through as required. The heater coils and the evaporator coils are practically touching each other. When you set the temp midway, you are in actual fact allowing the heated engine water to flow through the coils which results in the heater coil, which is very close to the evap coil, creating "hot spots" on the evap coil and that results in the evap coil leaking. He says that in the old days a thermostat used to cut on/off the compressor, but that is not the case anymore and the compressor cuts off only on high head pressure. I find this very hard to accept and find the whole system rather ridiculous if it is in fact setup in this manner.

He states the only way to stop that is to either turn the temp to full cold or disconnect/plug the heater water pipes going to the heater coil.

Now to maintain the cabin temp. from getting too cold he says switch the AC compressor manually as desired!!!

So my query is: Does setting the temp. at a comfortable degree (which is what it is supposed to be there for!!!) result in premature failur of the evap coil?

Views please.

Thanks in advance.

[the_maven]

Hi,

I own Punto emotion pack (MJD). This is related ACC in punto.
Rear seat passengers complain that AC is not enough (I generally keep the blower at 2-3 points less than the max and temperature set to ~20).

Is this common problem with Punto MJD? Does adding sunfilms improves this? If so, any suggestions for sunfilms/pointers.

I am under the opinion that ACC maintains same temperature through out the cabin and it might have some sensors to measure temperature at different parts of cabin and adjust air-flow (top/front/bottom) accordingly. Am I expecting too much from ACC of Punto?

Thx!

[.anshuman]

The normal tendency of most owners with cars without climate control is to keep the thermostat at coolest position and alter the fan speed to control the temperature but with Automatic climate control if you increase the temperature and reduce the airflow the car is ought to get warmer, Whilst the front seat passengers have airflow they wont complain its the rear seat passenger who will suffer.

Its not a problem with the car, you need to get used to using Automatic climate control system. The performance of Ac in Punto is adequate. Yes adding good quality sunfilm will reduce load on the airconditioning system.

For best performance and uniform cooling use it in full auto mode where the user only adjusts the temperature and rest of the variables like fanspeed, direction of flow et. are set automatically by the ACC.

[anachronix]

And dont forget to close the ventilator as well. The ventilator is ON by default and you would not get the temparatures low quickly!

[GTO]

[quote=the_maven;1590724Rear seat passengers complain that AC is not enough (I generally keep the blower at 2-3 points less than the max and temperature set to ~20). [/QUOTE]

The GP has a rather good air-conditioner. We drove it on a hot June day (car without tints) and it kept 3 of us cool. The problem you state extends to any car that doesn't have rear air-con blowers. Get some good quality sunfilm installed.

[AlokSriva]

Seems it has become a habit for me to bump up old threads oflate

Anyway, moving to the precise question - I am trying to understand whether an Auto Climate Control in Captiva having vents only on the dashboard would be more effective in cooling the cabin or would the vents in each row of Endy would create more cooling impact?

Additionally, it seems to me that an Endy's manual/regular AC would cool the cabin faster as compared to auto of Captiva (again, on account of multiple vents).

Help please

[GTO]

Originally Posted by AlokSriva

I am trying to understand whether an Auto Climate Control in Captiva having vents only on the dashboard would be more effective in cooling the cabin or would the vents in each row of Endy would create more cooling impact?

Additionally, it seems to me that an Endy's manual/regular AC would cool the cabin faster as compared to auto of Captiva (again, on account of multiple vents).

Firstly, cooling capability has nothing to do with the control unit (i.e. climate control or manual air-con switches). It is dependent on the components used (compressor, condensor etc.), air flow design, green house etc. Climate control merely helps to maintain the desired temperature. It does NOT increase the cooling capacity of any air-conditioning unit.

In an SUV, dedicated airvents for the 2nd and 3rd rows are a decidedly superior solution to having only those on the dashboard.

[AlokSriva]

Originally Posted by GTO

In an SUV, dedicated airvents for the 2nd and 3rd rows are a decidedly superior solution to having only those on the dashboard.

Thanks GTO! So it finally boils down to the vents and their positioning in the cabin which would decide the cooling effectiveness (over and above the other components listed by you).

That sure helps.

[shantanumishra]

Just came across this thread, although it is an old thread with dippy giving an excellent detail about ACC/AC comparison, just wanted to further add my 2 cents,

In normal AC, you might have to regularly increase or decrease AC Temp/Fan Blower speed depending upon the outside Ambient Temperature as also whether you have started feeling cold or is it getting hot, whereas in ACC, the set temp is maintained and you might never feel the need to change these settings, It not only maintains the temp, but also the Air flow and also distributes the air flow from all Vents available and not just the front vents.

An ACC also has an Auto Defrost mode, an ACC car has sensors all across the car including Rear Windshield, Front Windshield, Dashboard, etc. It can sense Mist on the rear and front windshield and once set on Auto mode, it can effectively remove and clear the same without any change of vent positions and settings, also, while doing so, the front dashboard vents would still be used to throw out normal air,

An ACC also helps a lot in Winters, In cold places on using a normal AC, you often require hot air from the front vents, you change the settings to HOT and blower speed, however, after some time, hot air becomes intolerable and you need to either slow down the blower or switch it off, whereas in ACC, this situation never arises, you can comfortably set the temp to 24 and enjoy your drive rather than worry about the hot air coming from the front vends, because the front vends in an ACC would blow normal temp air and the hidden vents would gradually increase the temp of the inside of the car to the set temp.

[devansn]

Does automatic climate controls improve the fuel efficiency? Would the compressor turn off and on automatically depending on the required and current cabin temperature? Or would it continuously run?

Since people agree that sun films help improve fuel efficiency, I am tempted to believe that the compressor would be automatically turned on / off by the ACC as per the required temperature.

[gavinimurthy]

The compressor turns off once the set temperature is achieved. It again starts when the temperature inside the cabin increases by a pre determined amount. Say you set the temperature to 25 degrees. Once the cabin cools down to 24 degrees the compressor switches off. It starts working again when the temperature rises to 26 degrees. Even while using the Automatic Climate Control the compressor does switch on and off if you set your cabin temperature to less than that of outside.

If the outside temperature is lower than your set temperature (in winters, places like Delhi) the compressor won't switch on. The heat generated by the engine is diverted inside and the temperature is controlled by opening and closing of the vent flaps as required.

You should get better FE in winters than in summers while being comfortable. :-)

Murthy

[ph03n!x]

Originally Posted by Mohnish

...There is no thermostat to cut on/off the AC compressor to regulate temp. The temp is controlled by flaps that allow the hot / cold ait to pass through as required. The heater coils and the evaporator coils are practically touching each other. When you set the temp midway, you are in actual fact allowing the heated engine water to flow through the coils which results in the heater coil, which is very close to the evap coil, creating "hot spots" on the evap coil and that results in the evap coil leaking. He says that in the old days a thermostat used to cut on/off the compressor, but that is not the case anymore and the compressor cuts off only on high head pressure.

Any thoughts on this post - more so on non-ACC cars? Is there a thermostat to cut off the compressor when a specified (set using the dial) temperature is reached?

I usually drive the car setting it about 1/3rd in the cold zone, with blower set to 2 (and later to 1 when it gets cold enough) - does this mean instead of cutting off the compressor, all my car is doing is diverting hot air mixed with cool air to maintain the temperature?!!

[devansn]

Originally Posted by gavinimurthy

The compressor turns off once the set temperature is achieved.

Murthy

Originally Posted by ph03n!x

Any thoughts on this post - more so on non-ACC cars? Is there a thermostat to cut off the compressor when a specified (set using the dial) temperature is reached?

I usually drive the car setting it about 1/3rd in the cold zone, with blower set to 2 (and later to 1 when it gets cold enough) - does this mean instead of cutting off the compressor, all my car is doing is diverting hot air mixed with cool air to maintain the temperature?!!

Mohnish was specifically talking about his Merc, I guess. Then the way ACC works is different in different cars?

[devansn]

Missed this in the earlier post:
In my dad's Spark, I have noticed that its performance is directly proportional to the AC fan speed. If I put it on the fastest position (4 I guess), there is a significant power loss compared to position 1. However, I have never felt that even when the AC switch is ON, the load on the engine is different in different cabin temperatures.

Similarly, has someone noticed engine load differences happening on and off depending on the cabin temperature in ACC mode? May be in bigger engine cars, this may not even be noticeable.

[Dr.AD]

Originally Posted by shantanumishra

An ACC also has an Auto Defrost mode, an ACC car has sensors all across the car including Rear Windshield, Front Windshield, Dashboard, etc. It can sense Mist on the rear and front windshield and once set on Auto mode, it can effectively remove and clear the same without any change of vent positions and settings, also, while doing so, the front dashboard vents would still be used to throw out normal air,

Is this "Auto Defrost Mode" standard for all ACC cars? Somehow I have not noticed this in many Indian cars which have ACC. For example, in SX4-ZXi, there is an ACC but I did not see this Auto Defrost Mode there. So does this happen by default (in ACC cars) without having to select this mode, or is this an additional feature of ACC which is there in only a few cars with ACC?

Thanks,
-AD