[Raghu M]

This is a great thread. I have had a problem with my AC just before trying to sell it off. I thought, it would be prudent to get the repair done and then hand over my car so that the buyer has a great experience with car. The AC stopped cooling and turned out the radiator fan was also gone. The AC works guy first told me that will check the AC gas and then if there is a leak, when the gas and leak status are confirmed, he will take further action. He was patient enough to clarify all my doubts. He checked the gas and found that it was gone, then he checked for a leak. Luckily there was no leak, the process to check the leak took around 45 minutes. After that they refilled gas and replaced the radiator fan. It was working like magic again.\

While I had a good experience, not everyone does. My question is, can someone share the gauge readings that are taken to check if there is gas or not in the AC unit. It can be for the home installed ones too. 90% of frauds on AC repairs are done by wrongly stating the gas measurements and the customer is forced to go for a refill even when not necessary. All the UC technicians that come have that gauge, they put it to the compressor and say the gas is low, you need to refill. 90% customers ask what to do and then the technician magically says he has the required gas and that it will cost between 1500 to 2500 for a refill. Same goes for cars as well. The worst part is, they say they can't guarantee a leak after we leave the garage. Can someone please throw some light on how to check readings on the gas levels. Thank you.

[bikertillidie]

Originally Posted by Raghu M

Can someone please throw some light on how to check readings on the gas levels. Thank you.

You need to hook up a dual gauge manifold to the high and low pressure service ports on the air conditioning system.

Please refer temp pressure charts for R134a below for "correct " values.

http://rechargeac.com/how-to/ac-system-pressure-chart


Any deviation in observed readings from these values require further troubleshooting / and perhaps necessitates a separate thread of its own

[s10]

Thanks @vigsom, a very informative thread. This explains the car AC in full details and you seem to have very in-depth understanding on them.

A noob and a bit of off topic question, typically car ACs are very robust as compared to home ACs where we see leakage quite often. In my areas we get leakage[on home ACs] almost every year and the AC guy always blames it to the drain nearby.
But car is also parked and driven in the same area but they don't get the same problem every year.
Do car ACs have anything special to them? Even car ACs have aluminium grills whereas home ACs have copper ones which are inherently more efficient. Is it copper which is more corrosive in this environment as compared to aluminium. Should I switch my home ACs also to aluminium

Any specific reasons or thoughts on this!

[jithin23]

Wow! What a thread!

You have explained the concepts and components of an Air-Conditioning system very well. Seriously, Team-BHP is like a goldmine for most of us to understand automobiles without an automobile engineering degree

[HooghlyBoy]

Originally Posted by s10

In my areas we get leakage[on home ACs] almost every year and the AC guy always blames it to the drain nearby.
But car is also parked and driven in the same area but they don't get the same problem every year.
Do car ACs have anything special to them? Even car ACs have aluminium grills whereas home ACs have copper ones which are inherently more efficient. Is it copper which is more corrosive in this environment as compared to aluminium. Should I switch my home ACs also to aluminium

Any specific reasons or thoughts on this!

Dear S10, I also faced the same problem in my Daikin made Home AC. I used Clear Guard Copper Preventive Coating" from Delhi-based Automotive Solutions in 2017 and the problem hasn't come back.
You can order from: https://www.automotivesolutions.net....e-coating.html
I heard from AC Technicians that some of the AC Brands give this coating at factory. Also Copper Coils less likely to be corroded than aluminum coils by refrigerant gas.
Hope this helps.

[luvurride]

Well described article! Thanks for sharing your knowledge and wisdom.

I have been facing a peculiar issue with my X1. The A/c when turned on throws a weird smell for 5 mins and then goes back to being normal. This usually happens in cold start and also when the car has been idle for more than 5 hours. I have never ever faced this in the previous 5 cars that i owned, Corolla 2006 being one of them which still works like a charm.

The BMW technicians cleaned the filters, checked everything and say there is no issue from their end and it could be sweat/residue in the blowers that could be causing the odor. They don't have an answer when I countered how I never faced it in my other cars.

Any pointers will help as I hate those initial 5 mins in the car!

[sdg4wheels]

Originally Posted by vigsom

Basic Components of a car air conditioning system

The following short video provides a quick overview of the components of a car air-conditioning system (please ignore the pressure ranges mentioned in the video – the low pressure side would be a typical 25-40 psig while the high pressure side would typically read 150-200 psig)

Thank You vigsom for the really detailed and informative thread . I wanted to ask you one small thing. I have a Chevrolet Tavera which does not have a cabin air filter as it is a model from 2006.I wanted to know if there is anyway to install a cabin air filter and if there is it should be installed where? Also Tavera never came with it so will it cause any harm if I try to install that?

[mmxylorider]

A professor in college had explained air-conditioning by using a deodorant can. On releasing the deo, can becomes cold to the touch. Now if the released deo were to be put back into the can (in compressed form), it would become a continuous cycle. The basic principle remains the same.

I will suggest two things for the car AC.
1. In winter months, do engage the AC every few weeks to ensure that the parts are not jammed up. Of course, this should be done once the engine is started and the engine bay is reasonably warmed up
2. Since the purpose if HV and AC, where it is not just cooling but also conditioning (humidity control), it is essential that the system works in removing moisture from inside air, especially during rains or moist conditions.

[Neversaygbye]

Originally Posted by vigsom

Basic troubleshooting of a car air-conditioning system

Thank you for this wonderful thread. I read in one of the posts that the ECU also cuts off under hard acceleration. In my car on long highway drives at speeds consistently between 80-100 kmph after about 2-3 hours of constant driving the AC stops cooling. If I shut it off for about 10-15 minutes, it again starts working. Could it be because of this reason? I do not have this problem in normal city or highway driving with variable speeds below 80. I spoke with my SA and he said that its probably nothing but the ECU trying to protect the engine. Did a trial highway run of 50 kms at high speed with him to show him the issue and the AC worked perfectly throughout. Anyway thereafter he adjusted the thermistor based on just our discussion but I am yet to test out whether that has made any difference (no highway drives during lockdown!). Is this issue normal?

Originally Posted by HooghlyBoy

Also Copper Coils less likely to be corroded than aluminum coils by refrigerant gas.

I second you on this. Also with copper coils they can be repaired by welding and usually withstand the pressure of the gas better and don't develop weak spots that easily. So it is always better to go for a full copper condenser if budget permits. I learnt it the hard way - had bought two ACs of the same brand together in 2003. The one with copper condenser is still going strong while the one with aluminum had to be sold as scrap 5 years ago.

[vigsom]

Originally Posted by mohitchalla

detailed thread on aircons.

Thank You @mohitchalla. I could have packed more into this but then Mission Demystify would have got defeated

Originally Posted by Jeroen

These days there is also R437A

Thank You, @Jeroen, for all those super valuable points that you made. R437A is the "retrofit" refrigerant for use in older cars that used to run on R12, while the retrofit for R134a is R1234yf, which I think is the standard refrigerant in Europe since 2011.

I think the variable reciprocating compressor is most used

Quite true; many cars are moving to the variable displacement type compressors withECV

When it comes to AC maintenance: I honestly don’t know how the big dealer garages in India work.

Large authorised service centers and large automotive workshops invest in the A/C refrigerant and oil recycling machine, commonly known by the name Robinair. In India, release of refrigerant to the atmosphere is declared serious only on paper, and that is why people still carry on by releasing refrigerant to the atmosphere, and then evacuate, and charge refrigerant using manifold gauges and cans of refrigerant.

Originally Posted by Reinhard

easy to understand

Thank You, @Reinhard. I tried to make the read as lucid as I could.

Originally Posted by sagarpadaki

1. The AC filter is the best insurance for the entire cooling system. The filter ensures that the evaporator coil behind the dashboard remains clean.

2.Whenever the car is washed, clean the condenser as well.

The above two must be the first step of diagnosis in troubleshooting the insufficient AC cooling.

Absolutely, @sagarpadaki. The filter is indeed the best insurance for the evaporator

Originally Posted by Tgo

I find it very disconcerting to see people sit in the car, turn the ignition on, with the blower starting at full blast

Not a good practice, @Tgo. The car should be started up with zero electrical load, and then the stereo, AC, headlights may be switched on as required.

have noticed that no matter what the temperature setting is in my Duster, the compressor has a 8 Sec On - 8 sec Off cycle. Temperature control is mostly just a blending of hot air from the heater core.

Agree on the blending part, which kicks in when ambient (outside air) temperatures are low. In hot weather, there is no way the blending will happen. I have found the compressor on time reduce if the blower speed is reduced for the same temperature setting. In fact, on ACCs, the blower speed can be set on Auto to achieve the most optimum compressor on time.

Originally Posted by bikertillidie

Most ac repair shops in India try to advocate replacement of expensive components rather than investigate the root cause/service components religiously.

Good to see you undertaking repairs yourself, @bikertillidie. You're right in your observations on most car A/C workshops.

Originally Posted by manishk123

why do Japanese cars have so much better air conditioning systems than European ones? Are the systems not designed for Indian conditions?

Thank You @manishk123. I haven't studied European cars in detail, but can definitely say that their ACs, especially the ones in VAG cars aren't designed to handle our harsh conditions. It is also possible that the "leathery" upholstery material absorbs more heat, plus the glass area is more. Can't say this emphatically, though.

[Mortis]

Originally Posted by luvurride

Well described article! Thanks for sharing your knowledge and wisdom.

I have been facing a peculiar issue with my X1. The A/c when turned on throws a weird smell for 5 mins and then goes back to being normal. This usually happens in cold start and also when the car has been idle for more than 5 hours. I have never ever faced this in the previous 5 cars that i owned, Corolla 2006 being one of them which still works like a charm.

The BMW technicians cleaned the filters, checked everything and say there is no issue from their end and it could be sweat/residue in the blowers that could be causing the odor. They don't have an answer when I countered how I never faced it in my other cars.

Any pointers will help as I hate those initial 5 mins in the car!

Hi. This usually happens due to mold formation on the evaporator coil inside the dashboard. The best solution for you would be after a long drive, turn the A/C thermostat to the max highest (hottest) temperature i.e. heater mode and the fan speed to max and drawing in outside air. Leave it like this for atleast 15-20 minutes with the windows cracked open an inch and vents pointed away from your leather seats. Turn it off along with your car and leave it to cool for a few hours or ideally the next morning. Then spray a can of 3m Air Conditioner cleaner into the vents using the extension tube and following the instructions. Then run the A/C as normal and it should be much better or eliminated totally.
Repeat the heat treatment every once in a while and the 3m treatment every year or so.

[vigsom]

Originally Posted by Raghu M

can someone share the gauge readings that are taken to check if there is gas or not in the AC unit

Thank You, @Raghu M. Easiest way to check for low refrigerant charge - compressor low side(suction) line closer to the engine firewall should feel like 10 degrees.C when the compressor is on. On touching, it should feel like a super chilled soft drink can. A low side gauge reading of 20 or less is another indication.

Originally Posted by s10

In my areas we get leakage[on home ACs] almost every year and the AC guy always blames it to the drain nearby

Thank You @s10. The argument given by the technician may be true if the AC outdoor unit is continuously exposed to some corrosive gases from the drain. Do other metal structures around see corrosion?

Aluminium condensers aren't my preferred choice for a home AC. They leak in 3 years in coastal areas. I had to change the condesner on my 2013 Samsung to copper in 2016; going good since then.

Originally Posted by jithin23

Team-BHP is like a goldmine for most of us

Thank You @jithin23. Content on team-bhp is rich in most departments, but deserves to be richer.

Originally Posted by luvurride

The A/c when turned on throws a weird smell for 5 mins and then goes back to being normal

Thank You, @luvurride. What @Mortis has recommended is spot on.

Originally Posted by sdg4wheels

I have a Chevrolet Tavera which does not have a cabin air filter as it is a model from 2006.

Thank You, @sdg4wheels. As far as I know, the Tavera doesn't have a provision to install a cabin air filter. If I remember right, the fresh air intake flap is right above the blower, hence a filter cannot be retrofitted. What you can do is to ensure that the fresh air flap is never opened, because that's where twigs, leaves, rat droppings can get in. The cooling coil is located just behind the glove box cover, and the fan resistor(Part with a wiring coupler) can be seen on the path from the blower to the coil. If you remove this resistor, you can view the cooling coil, and maybe use a fine brush or something and remove whatever loose debris there is.

Originally Posted by Neversaygbye

In my car on long highway drives at speeds consistently between 80-100 kmph after about 2-3 hours of constant driving the AC stops cooling. If I shut it off for about 10-15 minutes, it again starts working

Thank You, @Neversaygbye. The issue you've reported points to the electromagnet getting slightly weak. It heats up over time, weakens, and stops engaging the compressor clutch. Leave the AC off for sometime and it starts working again. An electromagnet on its last leg will stop engaging the compressor clutch within 15 minutes of switching on an AC. I've faced this issue on 2 of my cars so far.

You could reduce your blower speed once the cabin cools down sufficiently. That might help in giving the electromagnet some breather.

[TrackDay]

Great Thread. Thanks for put out a nice and well detailed thread on car air conditioning system.

Two points I always follow for maintaining the AC unit in my cars are :

1. Always switch off the AC unit before switching off the car, at least a minute before. Similarly after the starting the car, I wait for a minute or two for the engine to warm up before starting the unit.

2. Cleaning the air filter whenever possible. Not only does this give out more clean air, but also reduce stress on the AC unit. With newer cars this is easy, however with the older cars where the whole dashboard has to be removed, it can be difficult.

One of the advise I have received from an old friend for the manual type car AC is to either keep the cold/hot knob in the extreme cold or hot position and never in between. Is there any truth to this ?

[RGK]

Fantastic thread with lot of info ..

I follow this method religiously. After starting the engine, I wait for few minutes (fasten seatbelts, set mirror position, personal touch up etc) and then switch on the AC with the temp set at 24 deg. The car has ACC and the fan speed gets adjusted all the time.

Whenever I park, I switch off the AC and then wait for 2 minutes before shutting off the fan completely and then the engine. Is this a correct procedure ?.

As per my latest service report, the SA had remarked that my AC compressor has a minute leakage near the o ring (refrigerant qty was just 250 gms instead of 600 gms) and may need a compressor replacement (no child spare availability for Ecosport). I do not agree and planning to take it to an AC garage.

Guru AC service, CIT Nagar, Chennai do a very good job and let me try Prajeesh Aircon at Trichy (Dindugal road) if the present situation becomes normal.

[jeevan_61]

I have a weird issue with the AC on my 2011 Ford Figo diesel.
The AC seems to work absolutely fine and is a chiller if it turns on. But sometimes, it fails to turn on. the blower blows air, but the compressor doesn't run and there is no cooling.
I can tell that the compressor doesn't turn on as there will be a slight increase in the idle rpm and the car is slightly less responsive. Also, There will be a slight suction like sound and then the cooling starts when the AC works, or else just the blower just blows air and there is no suction sound. There is no issue with the cooling capacity or cooling speed when the AC runs, so I do not know what to suspect here.
I cant seem to demonstrate this issue with the mechanic as the issue occurs randomly and is totally unpredictable.
The issue seems to crop up more frequently when the car sits idle for a long time.
P.S:- I'm a newbie to team-bhp and do not know if this is the right place to post this, I would be glad if someone can shed some light on this.