[Maneesh]

Previously I used a Maruti 800, Indica DSL and now using Lancer Diesel. All these car's A/c compressor will take its trip-off whenever it reach a particular cabin temperature according to the blower setting. In Indica,the cut-off will happen if we press the accelerator pedal fully for a quick higher power requirement too. In my experience a/c cut-off functionality is there in both petrol & diesel cars.

[Jaggu]

Originally Posted by Sss

The compressor in Ritz - Diesel is of Variable Displacement type, hence may not trip.

So is this the real reason for the phenomenon?

[Sutripta]

Originally Posted by Sss

The compressor in Ritz - Diesel is of Variable Displacement type, hence may not trip.

Most of the other petrol vehicles have Fixed displacement in either piston or scroll type technology. Hence they trip once the desired cooling is achieved.

Hi,
Thought the Z version of both (with ACC) had VDCs.

Regards
Sutripta

[govigov]

Originally Posted by Sss

The compressor in Ritz - Diesel is of Variable Displacement type, hence may not trip.

Most of the other petrol vehicles have Fixed displacement in either piston or scroll type technology. Hence they trip once the desired cooling is achieved.

In Variable displacement type compressor the pumping capacity of the compressor can be varied from 6% to 100%, depending upon the load on the AC unit.

What are the advantages of the variable volume displacement compressors?

[Aroy]

Originally Posted by govigov

What are the advantages of the variable volume displacement compressors?

The advantages are that the compressor need not switch off regularly. The temperature is maintained by regulating the gas rate in the system, so that at high rates the cooling (and there fore the load) is high, while at low rate the cooling is less. You get air at a constant temperature in this system, unlike the normal AC where it is either chilling cold, or when the AC is off at the cabin temperature. The only problem is that if the cooling required is less than the minimum rate for the compressor it will super cool and there after form ice. So even in this system you need a cut-off switch, which I think is not provided in some cases.

The principle is same as that of VRF (Variable Rate Refrigerant) AC, or to the "Inverter" AC systems, where the motor slows down to reduce the gas flow, hence cooling, except that as the speed cannot be regulated in a car, the gas flow is regulated by changing vane geometry.

[esteem_lover]

Originally Posted by mayankjha1806

Yes it does cut off for various reasons. In my old Indica it used to cut off AC when the driver needs more power from engine (i.e. while accelerating hard it used to cut off AC). In my Baleno it cuts of AC after some time when the cabin get cooler (Climate control).

I do not have experience with the Indica (was it petrol or diesel ?) I agree to the Baleno and the million other cars here, they switch off faster when the blower is in 1 or 2 depending on the climate outside, climate control aside.

Originally Posted by Jaggu

Yes DDiS does not have compressor cut off based on temperature. It just stays ON all the while. I feel this is to avoid the jerks when a compressor kicks in and out. When you switch ON the AC the ECM changes the fuelling in DDiS and compensate for the power loss, also at idle you will see compensation of about 500 rpm.

Long back i had checked with one of the service advisers and they also did not have anymore info than this.

Jaggu, do you know this for sure ? What difference does the jerk make in a petrol or diesel, AFAIK, diesels can handle these jerks much better than petrol engines. More than that, I really am not sure about a 500 rpm in rise in diesel engines compared to only 200-300 rpm in petrols. Please do not bring the SA's remakrks, you will know better than them about the cars and their workings, I am sure of that.

Originally Posted by Figopian

If you stand outside the vehicle with A/C switched on, you could hear one hissing sound, I am assuming that is A/C compressor sound and it does go away for a while intermittently, that is the reason for me to consider that the A/C compressor goes on/Off in my diesel Figo. Could it be the evaporator/radiator fan? I don't know, if that fan will make this kind of hissing noise.

You will hear the hissing noise only when you are inside the car, outside the car it will be whirring high speed fan noise which is much louder than a hissing noise, so no comparison there.

Originally Posted by fiery enzyme

I have not had an issye for the last 10k kms including a 1300km non stop drive.

How the hell did you manage a 1300km trip NON STOP ? May I know ? No breaks for the compulsive relaxations ? None at all ? Then I have to give you the crown Bala.

Originally Posted by fiery enzyme

Actually in non climate control cars ie: the ones with the manual knob, keeping the knob at minimum or maximum does not make the compresseor cut off. What happens is that the hot air which derives the heat from the circulating coolant (not exactly sure how the heat is transferred I think the pipes run close enough or around it) is stored in a seperate pipe. when you adjust the thermostat to medium, this hot air gets mixed in the vents.

You can find this hot air pipe for the Figo above the front passenger footwell. Keep the car running and feel around next to the glove box. you fill find this.

No, it is not about adjusting the cool/hot knob, it is the blower speed that we are talking about here, at least that is what I think.

[TaurusAl]

Originally Posted by Aroy

The principle is same as that of VRF (Variable Rate Refrigerant) AC, or to the "Inverter" AC systems, where the motor slows down to reduce the gas flow, hence cooling, except that as the speed cannot be regulated in a car, the gas flow is regulated by changing vane geometry.

Good info, but then wondering is it really better than the normal thermostat method to control the cooling ? I mean in a car or even at home, when the compressor is left 'always on', its bound to burn more fuel right ?

Keep in mind that Maruti gives fuel economy a lot preference while designing cars.

[Jaggu]

Originally Posted by esteem_lover

Jaggu, do you know this for sure ? What difference does the jerk make in a petrol or diesel, AFAIK, diesels can handle these jerks much better than petrol engines. More than that, I really am not sure about a 500 rpm in rise in diesel engines compared to only 200-300 rpm in petrols. Please do not bring the SA's remakrks, you will know better than them about the cars and their workings, I am sure of that.

100% sure, when AC switch is activated apart from the RPM increase, ECM changes the fueling also. This can be noticed if you are driving the car and switching the compressor ON, engine will bog down for less than a sec and then resume, at the same time as compressor kicking in.

[Aroy]

Originally Posted by TaurusAl

Good info, but then wondering is it really better than the normal thermostat method to control the cooling ? I mean in a car or even at home, when the compressor is left 'always on', its bound to burn more fuel right ?

Keep in mind that Maruti gives fuel economy a lot preference while designing cars.

Actually at least in mains powered AC, a lot of power is wasted every time the motor starts. Then when the AC compressor motor slows down, it consumes less power. So in effect the VRF systems consume much less power while at the same time giving more or less constant temperature air.

Same principle goes in car AC. When less gas is being compressed, the load is less, so power consumed is less. In my opinion the constant temperature in such system is more conducive for comfort, especially if you are alone and the air is blowing directly at you.

[Sutripta]

Originally Posted by govigov

What are the advantages of the variable volume displacement compressors?

Originally Posted by TaurusAl

Good info, but then wondering is it really better than the normal thermostat method to control the cooling ? I mean in a car or even at home, when the compressor is left 'always on', its bound to burn more fuel right ?

Keep in mind that Maruti gives fuel economy a lot preference while designing cars.

In another thread
http://www.team-bhp.com/forum/techni...ml#post2570576

On - Off cycling will span the desired set point. This is less desirable than being at the set point (which admittedly can be a very difficult task).

Re: fuel consumption. Off hand answer is 'no'. But requires a few qualifiers.

The primary goal of a HVAC system should be comfort. (Of course assuming health and safety norms are met).

Regards
Sutripta

[sweet_poison]

hi guys, i think the following is the basic operating principle of HVAC systems in vehicles.

The compressor is run with a clutch system connected to the engine. The compressor is engaged/disengaged depending on the desired thermostat/thermometer and relative humidity sensor outputs.

Now for the question of why this is seen more in petrol cars than in the diesel versions, i feel its got to do with the engine rpm. The petrol cars have got a higher high end rpm (~6000 rpm) where as in diesel cars the rpm goes upto 4500 rpm approx. Higher the engine rpm= higher the compressor rpm = lesser time to cool. Once the desired temp and humidity is reached the compressor is disengaged. So once you rev up, petrol cars have higher rpm and hence the compressor is cut off more quickly.In diesel cars also, this phenomenon occurs but it takes more time.

So i think its more related to the engine rpm.

[Aroy]

Originally Posted by sweet_poison

Now for the question of why this is seen more in petrol cars than in the diesel versions, i feel its got to do with the engine rpm. The petrol cars have got a higher high end rpm (~6000 rpm) where as in diesel cars the rpm goes upto 4500 rpm approx. Higher the engine rpm= higher the compressor rpm = lesser time to cool. Once the desired temp and humidity is reached the compressor is disengaged. So once you rev up, petrol cars have higher rpm and hence the compressor is cut off more quickly.In diesel cars also, this phenomenon occurs but it takes more time.

So i think its more related to the engine rpm.

No exactly true, as the gearing ratio of the pulleys is different for lower RPM engines from those of higher RPM engines, both for AC and the Alternator. If it is a low revving engine the AC compressor (and the alternator) will run faster, if it is a high RPM engine they will run slower for a given engine RPM.

Both these devices can run as fast as you want them to, the limitation being the bearing, which have to be enhanced for high speed running.

[Sutripta]

There was another thread which has some discussion pertaining to ACs, which I forgot to quote.
http://www.team-bhp.com/forum/techni...ml#post2573941

[TaurusAl]

Originally Posted by sweet_poison

hi guys, i think the following is the basic operating principle of HVAC systems in vehicles.

The compressor is run with a clutch system connected to the engine. The compressor is engaged/disengaged depending on the desired thermostat/thermometer and relative humidity sensor outputs.

Now for the question of why this is seen more in petrol cars than in the diesel versions, i feel its got to do with the engine rpm. The petrol cars have got a higher high end rpm (~6000 rpm) where as in diesel cars the rpm goes upto 4500 rpm approx. Higher the engine rpm= higher the compressor rpm = lesser time to cool. Once the desired temp and humidity is reached the compressor is disengaged. So once you rev up, petrol cars have higher rpm and hence the compressor is cut off more quickly.In diesel cars also, this phenomenon occurs but it takes more time.

So i think its more related to the engine rpm.

Negative, in this case it should even affect the cooling time and the cooling performance. I confirmed with 2 more reliable sources, DDiS does not come with a compressor cut-off.

Now its winter and chances that there might be snowfall inside my Ritzy from a/c vents and my drinking water might solidify as well due to lack of a/c cut-off..

[krivbel]

I bought a Ritz VDI in march 2010. I have driven long distances many times over in my car. Even in the scorching summer heat, I have driven to Pune from Bangalore, and the AC had never given a problem. However, in May 2011, I met with an accident, my car was in the middle of a five car pile up, and my car took a beating in the front as well as in the rear. Ever since I got it fixed, the AC has been giving me problems. One of the first problems that I am facing is that the Blower keeps making the loud noice but no air comes from it after about 45 minutes of AC usage. Second problem is that the cooling, the AC stops cooling after about 45 minutes. I have had it fixed at Girimaji Enterprises, an authorized Maruti service center many times over, and every time they told me that it was a rat problem, and the Rats have been chewing the pipes, and cables. Even after they fixing the problem, the problem persists. Finally, a mechanic was referred to me, who apparently could fix the problems. He took the Car last week. He has done the following:

1. Completely Checking the AC system inside engine room, replacing defective hose, cleaning condenser etc, and refixing.

2. Completely Checking the AC system inside dash board area, cleaning blower unit, cooling coil, etc., and refixing.

3. Vacuuming the A/C system, checking and fill gas, and changing.

He charged about Rs. 8500 for the entire AC fixing Fiasco. He charged Rs. 3450 for the AC hose. I have mentioned the three things above as he has stated in the bill. Now my AC is still not fixed. Whether I raise a query with the mechanic or not is secondary. I need to fix the AC problem. Can anyone here help me as to what should be done? Do you know any one who can fix the AC in Bangalore? Would much appreciate any help.

Thanks.