How Does Air Conditioner Works in Cars?

[hemantprakash12]

Hi,

I want to know the working principle of air condition in my car (Swift). I read somewhere that compressor doesn't stop when temperature in increased from knob. Instead hot air from engine is mixed with cool air. Is is correct?

 

[bhvm]

Re: How does air condition work in cars?

The AC in cars work the same way it does in Home-
How Air Conditioners Work - HowStuffWorks
The refrigrant gas (usually R134A) is used. But rater than an electric motor driven compressor, a Belt driven compressor is mated to the engine via a Mini "Clutch" (you can hear the clutch sometimes like "Click....)

For the heater there are 2 types. In my old safari (1.9L 98 Model) the heater was electric. There were coils behind the dashboard and the temperature knob sent a particular voltage to the coils to generate hot air. It also had a separate Rear AC unit with the same coils.

Then My Indigo marina was different. There was a heat exchanger in the engine and as you said, Hot air from the engine is INDIRECTLY used to heat the AC Heating unit. This way we did not have warm air (In dire winter) until the engine warmed up a bit.
Also there was no Fine control over the temperature like it was in safari.

 

[dhoom9]

Re: How does air condition work in cars?

As opposed to all other cars I had owned or travelled, my Rexton has separate blower with air filter when I select cabin air to be reused in AC, default that blower is off & outside air is used always in AC.

 

[bhvm]

Re: How does air condition work in cars?

As opposed to all other cars I had owned or travelled, my Rexton has separate blower with air filter when I select cabin air to be reused in AC, default that blower is off & outside air is used always in AC.

same with my safari 3.0L. 2006.
you could hear the blower and airflow also increased. I don't see that in recent cars though

 

[kannan.cnkr]

Hi,

I want to know the working principle of air condition in my car (Swift). I read somewhere that compressor doesn't stop when temperature in increased from knob. Instead hot air from engine is mixed with cool air. Is is correct?

For you understanding this how a car AC system works.

 

[ameyam]

Ok, then the question that begs asking- if there is no auto control on the compressor, is it ON all the time. So, if I set to a higher temperature (or a lower cooling setting) in winter, will I save any fuel? Or is it better to switch the aircon ON and OFF once in a while?

Ameyam

 

[kannan.cnkr]

Ok, then the question that begs asking- if there is no auto control on the compressor, is it ON all the time. So, if I set to a higher temperature (or a lower cooling setting) in winter, will I save any fuel? Or is it better to switch the aircon ON and OFF once in a while?

Ameyam

Yes off-course in manual A/C when ac switch is on compressor will run as long as you switch off the A/C.

Temperature control nob will be connected to the HVAC condenser unit with two shutter door which will restrict the cooling flow from the condenser due to this cool air will be limited. but the compressor will work on full speed no doubt in it.

In my point of Fuel eff will won't be there as A/C manual will be working all the time.

 

[Figoian]

Yes off-course in manual A/C when ac switch is on compressor will run as long as you switch off the A/C.

Temperature control nob will be connected to the HVAC condenser unit with two shutter door which will restrict the cooling flow from the condenser due to this cool air will be limited. but the compressor will work on full speed no doubt in it.

In my point of Fuel eff will won't be there as A/C manual will be working all the time.

That be the case, why does the Compressor get off & on often? I can at least feel it in Figo as it has the largest compressor in this segment and every time it goes on, gives a big vibration. I have observed it standing outside too. The sound varies with on & off.

 

[bhvm]

That be the case, why does the Compressor get off & on often? I can at least feel it in Figo as it has the largest compressor in this segment and every time it goes on, gives a big vibration. I have observed it standing outside too. The sound varies with on & off.

I noticed this in my safari (manual ac ) the clutch connects and disconnects the compressor. very noticeable at night.
however in my hyundai i10 it's always on. I guess Its a. manufactures preferences.

 

[Figoian]

I noticed this in my safari (manual ac ) the clutch connects and disconnects the compressor. very noticeable at night.
however in my hyundai i10 it's always on. I guess Its a. manufactures preferences.

Maybe! But I believe, it also depends on various other factors like ambient temperature, number of passengers, AC capacity etc. Safari's AC Compressor would obviously be of larger capacity than of i-10.

So, if that's actually cutting off, then it should save fuel too. Right?

 

[bhvm]

Maybe! But I believe, it also depends on various other factors like ambient temperature, number of passengers, AC capacity etc. Safari's AC Compressor would obviously be of larger capacity than of i-10.

So, if that's actually cutting off, then it should save fuel too. Right?

agreed. however I feel my i10 is going too cold. the compressor is not cutting off even at extremes (I can see fog coming from vents )

 

[yoscenario2000]

In my hatchback segment vehicle (New Gen Maruti Suzuki Wagon R VXI), I've observed the clicking sound of compressor as being ON/OFF (seems relay operating sound?), when blower speed is 1-2.

So isn't this the sign that compressor is being controlled and ON/OFF by temperature control relay as in our normal home appliances like home AC or Fridge ?

And if this is the case, I believe, then blower fan speed really playing a vital role in FE of a vehicle ?

Experts shed some light on this query, is fan blower speed is really affecting FE of manual controlled AC vehicle as we think?

 

[kannan.cnkr]

I too have maruti Ritz but the compressor run's always until i switch off the ac.

As for too my knowledge manual ac has no temperature sensor's to monitor the AC system.

If you take automatic climate control AC system it will monitor the inside temp and out side temp. so the system will control the compressor and fan system by a inbuilt control which will turn off/on the compressor by the set inside temperature but in manual AC we have the control of the FAN speed and temp control shutter knob.

So if you off the AC fuel eff will there else no Fuel is saved.

 

[yoscenario2000]

I too have maruti Ritz but the compressor run's always until i switch off the ac.

As for too my knowledge manual ac has no temperature sensor's to monitor the AC system.

If you take automatic climate control AC system it will monitor the inside temp and out side temp. so the system will control the compressor and fan system by a inbuilt control which will turn off/on the compressor by the set inside temperature but in manual AC we have the control of the FAN speed and temp control shutter knob.

So if you off the AC fuel eff will there else no Fuel is saved.

If it is the case, then what's that clicking sound I can hear and observe the increase/decrease load on the engine & the acceleration, whenever blower fan speed is 1-2, and occupants not more than 2 with no luggage city traffic.

 

[ameyam]

There is definately a system to regulate the compressor- I have heard the click in the Wagon R too- both in the old and the new one on the test drive

Being from the HVAC field, that compressor has enough power to convert the car to a fridge. That doesnt happen

If you drive the car in a lot of traffic like me you will have had this experience. Standing in traffic with the foot on the brake, there is a sudden drop in engine rpm and the brake pedal sinks in. This happens as a energy saving feature in an extended idle where the engine drops from 1200rpm or so to 700. But it also happens when the aircon disconnects when a set cabin temperature is reached. The load on the engine drops and the ECU reduces the rpm. Then the vacuum applied to the brake system reduces and the brake pedal sinks in

On the alto 800 CNG, there is a secondary effect where in the brakes dont apply as sharply with the aircon on. But thats a different matter.

If compressors didnt cutout off, their life would be very short. In an auto climate car, the cabin temperature and humidity is just controlled more accurately.
The real question is, if I set the aircon dial to a lesser amount of cooling- being winter now, will that save any fuel- will the compressor run for a shorter time or is hot gas from the engine used to reduce supply temperature to the cabin?

Ameyam