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Old 14th May 2015, 15:44   #76
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Default Re: Understanding Car Air-Conditioners

joybhowmik,

That problem has been solved now. It was due to faulty fan motor. We replaced it and engine heating is normal and a.c is working perfectly fine now. But there is a new problem (link below). Can you please throw some light on it?

http://www.team-bhp.com/forum/techni...ml#post3706356 (Engine & Turbo Woes - Chevrolet Optra Magnum)
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Old 19th May 2015, 10:41   #77
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Very nice thread!

I had a few questions regarding the A/c (auto-climate control) of my new Hyundai Fluidic Verna 4S:

The A/c works perfectly. But I feel that the compressor is on all the time, and never switches off, because:
  1. On the outside, I can hear the typical "A/c on" sounding engine all the time
  2. Having the A/c off, blower on, but temperature set to low on a hot day, still blows cool (but not cold) air
  3. I don't hear/feel the compressor turn on and off. In all the other cars I have driven, I could hear/feel the same.
  4. The RPM always hovers at around 820 (and not around 790) - typical of the "A/c on" state
Note that I cannot see the compressor inside the bonnet properly, so I cannot figure out whether the electromagnet that runs the compressor is actually activated or not.

Is this a problem? Is this how newer A/c's work?

Thanks in advance!
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Old 24th May 2015, 04:36   #78
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PearlJam: It would be best to get the A.C. Checked at nearest H.A.S.S. as its doesn't seems possible in any condition for A.C. compressor to remain ON all the time.

however as you state, sometimes A.C. gives cool air not cold, it seems the compressor is getting dis-engaged.

If compressor stays ON all the time, I don't think there's anything else which could blow cool and not cold air, what climate control setting does is, it helps in maintaining cabin temperature by limiting the amount of time compressor will run for.

Still it is advisable to get it checked for any error and faults.
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Old 24th May 2015, 12:00   #79
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Default Re: Understanding Car Air-Conditioners

@ghpk, thanks for your inputs. Yes, I will check with Hyundai on this. One more thing I observed is that the cooling fan only switches on when I switch on the a/c, so in that sense, the circuitry seems mostly ok.

However, I don't agree with you that cool air means that the compressor is getting disengaged. Modern systems use the heat from the engine for heating, and they can mix the heat with the compressor output to give optimum humidity and temperature.

Further research on this topic led me to a class of compressors called 'clutchless variable displacement compressors (not covered earlier in this topic), which are much more efficient that the traditional clutch type ones. There are 2 excellent articles that explain this:

1. http://www.audizine.com/forum/showth...late-vs-clutch
2. http://www.audizine.com/forum/showth...=1#post5913687

There's a nice video too:



However, I couldn't figure out whether the Hyundai Verna uses this type of compressor.

Last edited by PearlJam : 24th May 2015 at 12:06.
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Old 24th May 2015, 13:04   #80
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Default Re: Understanding Car Air-Conditioners

Dear Pearljam, as long as you have cold air blowing and the temperature setting works. You don't have a problem.

Just make sure the thermostat isn't faulty and the lines are icing up. If that's not happening your AC is working fine.
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Old 24th May 2015, 19:52   #81
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The AC in my 5 year old alto lxi has a weird issue. It usually works fine when the car is moving at speed and cools well but the problem occurs when say I am waiting at a red light with the AC on. The AC seems to run for say 15 to 30 seconds and then stops for some time before restarting again . Is it supposed to do that? Should the AC be starting and stopping this frequently. I always thought the compressor is supposed to run continuously.

Last edited by bullrun87 : 24th May 2015 at 20:10.
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Old 24th May 2015, 20:43   #82
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Originally Posted by bullrun87 View Post
The AC in my 5 year old alto lxi has a weird issue. It usually works fine when the car is moving at speed and cools well but the problem occurs when say I am waiting at a red light with the AC on. The AC seems to run for say 15 to 30 seconds and then stops for some time before restarting again . Is it supposed to do that? Should the AC be starting and stopping this frequently. I always thought the compressor is supposed to run continuously.

Sounds like your system needs a refill, thats all.
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Old 25th May 2015, 19:12   #83
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Originally Posted by bullrun87 View Post
The AC in my 5 year old alto lxi has a weird issue. It usually works fine when the car is moving at speed and cools well but the problem occurs when say I am waiting at a red light with the AC on. The AC seems to run for say 15 to 30 seconds and then stops for some time before restarting again . Is it supposed to do that? Should the AC be starting and stopping this frequently. I always thought the compressor is supposed to run continuously.
Yup, looks like you are running low on refrigerant. There is also a possibility that the condenser isn't getting cooled in stop and go traffic. Read: Faulty fan.
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Old 25th May 2015, 20:17   #84
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Quote:
Originally Posted by bullrun87 View Post
The AC in my 5 year old alto lxi has a weird issue. It usually works fine when the car is moving at speed and cools well but the problem occurs when say I am waiting at a red light with the AC on. The AC seems to run for say 15 to 30 seconds and then stops for some time before restarting again . Is it supposed to do that? Should the AC be starting and stopping this frequently. I always thought the compressor is supposed to run continuously.
My Alto LXi does this when the fan speed is at 1. Turn up the fan speed to 2 or 3 it does not do this. What speed are you using the blower? It seems that at low blower speeds the thermostat trips early.
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Old 25th May 2015, 20:20   #85
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Quote:
Originally Posted by bullrun87 View Post
The AC in my 5 year old alto lxi has a weird issue. It usually works fine when the car is moving at speed and cools well but the problem occurs when say I am waiting at a red light with the AC on. The AC seems to run for say 15 to 30 seconds and then stops for some time before restarting again . Is it supposed to do that? Should the AC be starting and stopping this frequently. I always thought the compressor is supposed to run continuously.

Possibilities in order from most likely to least likely:

1) low refrigerant (gas) level,

2) condenser fan malfunction,

3) ambient warm air mixing into the cooled air,

4) electrical fault with condenser fan relay/fuse,

5) fresh air door malfunction

Advised remedy:

Only one! Go to your Ac technician and get it fixed! I wouldn't suggest any DIY's here as the issue needs an accurate diagnosis with appropriate tools.
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Old 25th May 2015, 20:46   #86
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Originally Posted by techiecal View Post
. What speed are you using the blower? It seems that at low blower speeds the thermostat trips early.
Quote:
Originally Posted by pixantz View Post
Possibilities in order from most likely to least likely:



Only one! Go to your Ac technician and get it fixed! I wouldn't suggest any DIY's here as the issue needs an accurate diagnosis with appropriate tools.
I usually keep the blower speed at 2 and I think this happens at blower speeds of both 1 and 2. I am not sure I have ever used the blower on speeds 3 and 4 for prolonged periods, will have to see if the compressor trips at those speeds.
Thanks for the help pixantz , I shall take her to an AC specialist at the earliest. As far as I can tell the condensor fan is working fine. I don't think I have ever had the AC system serviced . Do you guys know how often should the AC be serviced?

Last edited by bullrun87 : 25th May 2015 at 20:54.
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Old 25th May 2015, 22:38   #87
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I don't think I have ever had the AC system serviced . Do you guys know how often should the AC be serviced?

The fact that you've not serviced your Ac for probably a long time, or never, adds another possibility of malfunction: clogged evaporator core(cooling coil), which causes the core to get over-cooled hence causing the compressor to cut-off prematurely.

The Ac should be ideally serviced once a year for optimum performance and longevity. Also, preferably the service should be done just before or at the onset of summer to have it in prime condition when it ought to be.
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Old 27th May 2015, 14:08   #88
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Originally Posted by anujmishra View Post
Recently, I fit the middle row AC blower in my Safari Lx and went for 5000+ Kms long drive to my hometown. In peak of summer the AC used to work quite comfortably during whole journey and it never troubled.

It is while returning just 250 KMs away Bangalore (near Tirupati) suddenly blower stopped blowing air. The blower motor was working as i could make out with noise but no air was coming in blower. Even in night at 9 PM it was very hot outside and we started sweating. I never drive with windows open even in city. I feel it quite uncomfortable due to pollution, noise and air.

I had to stop at that time for some break for 30 minutes as I was driving continuously from Visakhapatnam. After break, when I started again the blower started working little bit but the problem was still there. We reached home around 3 AM.

Next day, when I started car, everything was back to normal. Blower was blowing complete cool air. While searching google, I found out that might be thermostat went wrong, due to this ice crystal forms in cooling coil and in blower. I still have to get it checked due to other higher priorities of work. Will get it checked soon.

This is also one kind of failure one can face even without dirty cooling coil or leaked freon from system.


I had the exact same problem to my Tata Manza, Quadrajet Aura. EXACT same problem.

For some time, in Bangalore, the ac was working except that there was no air, or very minimum air coming out through the vents. Even at highest blower position. Went to a Ac mechanic and he said filter and coil are choked, and he cleaned it. Also filled in the gas. The ac was perfect. We went to kerala recently, and it gave no problem in the onward journey. While retuning, I had the very same problem as above. I have to switch of the ac for while, and it comes up after that. But for my daily use here, I dont face this issue. May be that I dont drive it for more than an hour, continuously.

Any pointers are welcome. Also note that the issue was while passing though very hot salem region (around 40 degrees). Has it something to do with the problem?

Thanks,
Venu.
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Old 29th May 2015, 00:32   #89
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IMHO the Auto Acs are not very compatible to our tropical type climates and very few or none of the cars available have it calibrated right to bring down the temp. drastically and stay that way. That's why the manual Acs feel more effective comparatively.

If your car is standing in direct sunlight and all of the interior is scorching, the ideal way would be to roll down all windows and wait for a minute or two or drive for about 30 seconds while simultaneously keeping only the blower on at slow speed to rid the insides of the ac of the hot air. Remember, cars standing in the sun with all windows closed, can have the interior temperatures coming to around 70deg! The plastics, air, fabric, everything! The best and fastest way to get rid of that is to ventilate with cool ambient air as described above. Your poor automatic ac tries to do this via a small vent which is about 4inch X 6inch in size at the most. That takes much longer plus loads up the ac a lot. Now after doing the above, please turn blower speed to full and Ac temp. to 'Cold' or 'Low' or the minimum coldest setting while also rolling up the windows. Now your cabin should start cooling down rapidly. If people are seated in the back seat please direct the flow of the two middle vents in between the two front passengers towards them. Especially for cars without rear vents. After you feel that the cabin is chilled enough you can set blower to first or second speed or as you like and set temperature according to your comfort. This is how you can manually get the best and fastest cooling out of your car ac on a hot day. You can switch to Auto later too.

Your auto ac does all of the above except for the initial hot air purging bit. You can help it by doing it manually and hence also relieving the ac of a lot of initial load.

A simple way to do it in Auto is: Roll down windows, press Auto(ac), press the recirculation button to recirculate mode, as you are letting in fresh air manually. You can start driving and roll up windows after about 20-30 seconds or so. That should do it.

Hope this helps and hope I was not too complicated.
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Old 29th May 2015, 00:39   #90
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Originally Posted by vrvarier View Post
I had the exact same problem to my Tata Manza, Quadrajet Aura. EXACT same problem.

For some time, in Bangalore, the ac was working except that there was no air, or very minimum air coming out through the vents. Even at highest blower position. Went to a Ac mechanic and he said filter and coil are choked, and he cleaned it. Also filled in the gas. The ac was perfect. We went to kerala recently, and it gave no problem in the onward journey. While retuning, I had the very same problem as above. I have to switch of the ac for while, and it comes up after that. But for my daily use here, I dont face this issue. May be that I dont drive it for more than an hour, continuously.

Any pointers are welcome. Also note that the issue was while passing though very hot salem region (around 40 degrees). Has it something to do with the problem?

Thanks,
Venu.
It's a thermostat malfunction. Also known as thermistor. The sensor that cuts-off the compressor when optimum cooling temperature is reached. The malfunction causes the evaporator core or cooling coil to over-cool and form ice which restricts air flow and stops the cooling.
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