Does anybody have good knowledge and experience with car air conditioning and can give me some steerage here?
About 2 weeks ago my car air con started playing up. It blows chilled air through the vents on the passenger side, BUT unchilled ambient temperature air on the driver side.
That suggests the compressor, condenser and evaporator are all working and there is refrigerant gas in the system.
But why is the chilled air only emanating from the vents on the passenger side, and ambient temp air on the drivers side?
Suggestions so far are that there may be rats nest in the air channels or the air venting valves which direct the air flow inside the system are not working properly.
That makes sense to me,âŠ
BUT a car air con service centre says the most likely cause is the system needs re-gassing.
My problem with that explanation is that if gas has been leaking out of the system, then the current problem would NOT have occured suddenly, but rather over a period of time, and secondly, how does a loss of refrigerant gas equate to chilled air coming from only the passenger side vents and not the drivers side?
Before I commit to spending $200 on having the system re-gassed, I would like to feel confident that I understand what is going on and not just blindly trusting an expert and coughing up $200 and finding this does not fix the problem.
I have replaced the cabin air filter but this has, as expected, not solved the problem
Not an expert but have experience with a Citroen C4 and conversations with the mechanics about same. Many if not most modern cars are running the compressors and mixing cold with hot for the temperature control. Some have air channels and flaps to manage the mixing and airflow into the cabin.
The C4 had two, one on each side. If a flap did not work it exhibited the symptoms you describe. The flap in the C4 was known to fail because the original was cheap nasty plastic and the gears wore down or broke off. The motor or control could also fail but that was uncommon in the C4.
I suggest you go to a dealer or a mechanic familiar with your make and model. My guess is your A/C specialist is selling more than fixing.
edit: the same control can be done with hot water valves. The compressor circulates cold through its pipes and hot water is controlled by a valve on each side for dual zone climate controlled systems. The air passes over the hot and cold pipes according to set temperature targets. If the hot valve on one side freezes open or midway it can overwhelm the cold and make it appear there is no cold, eg like ambient temperature. A way to determine if that could be relevant is whether there is cold on the drivers side immediately after start-up but then warms as the engine heats up.
I am in the ranks of the ignorant too on the niceties of car aircon but this makes no sense to me. There is only one compressor and one circuit of gas so if there is a compressor failure or loss of gas it will affect the whole system not just one side. There is something specifically wrong with the side that is failing. I agree another opinion is needed. Just for fun, what happens if you turn it to heating?
Believe it or not, there are more than a few posts on Web sites that explain that if the chilled core that the air blows over doesnât really get fully cooled due to lack of refrigerant, then air ducted to one side will be cooled, but the other side not.
But really, the whole environment control system with ducting, and mixing of ambient air, from outside, or inside, with warm air from the engine, or chilled air from the aircon compressor, and sensors, and blend doors, is the job of an automotive aircon expert.
Since a large percentage of aircon problems in cars is related to lack of refrigerant, probably a standard go to for a fix. A regular regassing is probably needed anyway as the stuff just leaks away over time.
I would find some information on your specific car make and modelâs system, and ask questions about terms.
Does your vehicle have independent controls for the driver and passenger? IE Dual Zone Climate Control.
P.S.
I had a longer reply but cut it back to this one question as there is different guidance if it is not.
The more spartan single control car AC uses a common/shared duct. A single blower fan, a common cooling core and a common heating core using waste heat from the engine. Closing the passenger side vents will force most of the airflow to the drivers side, since all is common.
Thank you everyone for all the suggestions.
My car is an unsophisticated Subaru and does NOT have dual climate controls.
Iâve tested all the suggestions.
Hot air emanates equally from all the vents both driver and passenger side.
The problem is the same irrespective of fresh or recirculated air.
Closing the passenger side vents does move the chilled air to the drivers side vents!
I would certainly like to see how the lack of gas results in this problem, if I could see the whole system in a cut away diagram, but I am loathe to spend my time removing the dashboard to have a look. The people at Repco suggested using a snake inspection camera to check the operation of the air control valves.
I dislike trusting âexpertsâ when I donât really understand the workings enough to be able to decide whether or not to trust them. And even more so if the said expert refuses to give me an explanation because they think Iâm stupid or donât need to know.
I will go back and interrogate the air con expert and see if they can offer me a believable explanation, and will also consult with another local expert and go from there.
Air con gas leaks out slowly and this problem occured very suddenly - so those facts donât add up to low gas problem in my mind, but maybe I might learn something here.
Thanks everyone
BB
But good luck trying to work out where the problem may lie.
From what you have said I agree with Repco. It does seem to suggest that a vent actuator (motor) isnât operating causing the driver and passenger vents to receive (value remaining open) warm air from the outside. This would mean that the warm air would only come in when the car is moving. When stationary, no air comes from these vents.
It could be an actuator which has failed, or the circuitry which operates the actuator (wiring connection lose, fault in the wiring loom such as a broken wire or a fault in the control board). Finding out the problem could be easy to difficult, depending what it is.
Aircon gas can leak out quickly (catastrophic failure), but, if it did, you wouldnât have any cold air from the centre vents.
If you arenât comfortable with the initial âexpertsâ you approached, have you tried another. An Auto electrician may also be able to help if it isnât the air-conditioning compressor or piping, but wiring/actuator/connector or circuitry issue.
Pardon my confusion but these two statements seem in conflict.
What chilled air if all vents blow hot air? The statement needs more context. That could be symptomatic of low gas but as you indicated a slow leak should result in a change over time, not over night unless there is a significant leak.
This may be helpful as it describes the basic system?
I hope we non-experts have provided enough information for you to ask the âexpertsâ the right questions. Please let us know what it was.
Dear PhilT
To attempt to alleviate the confusion, Syncretic Busted BS suggested turning it onto hot air and see what happens. The result of which is the hot air cometh equally from all 4 front of car vents (passenger and driver).
In cooling mode, with all vents open, cooled air only emanates from passenger vents - drivers side vents dispense ambient temperature air (either fresh or recirc) tested and verified with a special thermocouple thermometer. However closing the passenger side vents does change the situation and cooled air then comes from the drivers side vents.
The article âSubaru Air Conditioning Explainedâ was very interesting and the author comes across as knowing what he is talking about. Thatâs the sort of expert I like to deal with. He knows what heâs talking about and has no issue sharing his experience.
I will visit the local âexpertâ again next week and also another air con place and pick their brains before I commit to anything. Taking the dashboard apart to investigate the valves is not on my âlike to do listâ.
Perhaps I can train up one of the mice my cat brings inside and tell it to take a stickybeak through the air ducts and report back to me on the findings!
Anyway, thus far the problem has exposed a totally clogged cabin air filter which I have replaced resulting in increased air flow from the vents.
Nothing seems to be mentioned in the Subaru owners handbook about replacing the cabin filter and I would not have even realised it was there except for this problem provoking a closer look.
The owners handbook suggests taking the car to an authorized Subaru dealer for everything, even changing a light bulb. I find this a bit of a condescending attitude from Subaru. I am going to see if I can fix it myself and save a fortune, as are many other car owners, so Subaru would get more respect from me if they gave up their âtake it to the dealerâ attitude so we can make more money out of you, and gave some tips for DIYers who are going to have a go anyway no matter what Subaru says.
When the problem has been correctly diagnosed and fixed I will report back here on it.
BB
Iâve now consulted with a third air con repair outlet and now have three different and somewhat incompatible opinionsâŠ
The symptoms of the problem:
Chilled air emanates from passenger side vents only. Drivers side vents emit ambient (unchilled) air.
(heating cycle works properly and itâs NOT a dual climate control system).
Opinion #1.
The air control valves inside the system are jammed or not working properly. Or rodents have built a nest inside the ducts and this is blocking the air flow. I then suggested this would require the loathsome task of removing the whole dashboard assembly - urgh! But they said this can be checked using a snake inspection camera - no need to take dashboard apart (phew).
That opinion makes sense.
Opinion #2.
The system needs re-gassing. When I questioned how this could be, I was told that 9 times out of 10 regassing will fix this problem - the implication being that it is a common problem�?
Opinion #3.
âwe have never heard of this problem beforeâ!!!
Huh??
When I suggested that perhaps an inspection camera could be used to check the ducts, I was told that âNO the whole dashboard assembly needs to come outâ!!
This mob would start with re-gassing the system and if that doesnât fix it, they work from there!
This is why I refuse to blindly trust an expert until I have done my own research and feel as if I know enough about the matter to be able to make some sort of judgement in the best direction!
It also reveals that for those who have no technical know how or insights are at the mercy of trusting whoever claims to be an expert. Eeekkkkk!
When the problem has been successfully fixed, I will report on it again.
Weâve had critters (small marsupials) progressively move between our vehicles nesting. They are very capable of finding a way into the ventilation ducting.
Two telltale signs. One is critter droppings in the vehicle. Another if itâs a rodent in particular is a mouse like smell (assumes one has had pet mice at some point in life).
If you have not already done so it might pay to remove the cabin air filter and look for any signs of leaf, grass or droppings etc. A small mirror may be useful or your mobile camera at getting a look at the cross duct from the passenger side (typically where the filter and fan are) across to the drivers side. You may be in luck. A smaller GoPro might be able to look a little further.
Irrespective all 3 businesses are offering an educated guess. The most common cause of faults with automotive AC is a loss of gas (slow over time) or more rapid loss due to a leak. Hence they will be quietly sceptical until they have a proper inspection.
The greater difficulty for those responding is to answer the customer without actually seeing the fault for themselves. A competent licensed automotive AC specialist should be offering a fixed fee to inspect and test operation. IE to determine whether the system is low on refrigerant gas before draining the system. Thereâs little point in refilling a system if there is a leak or component fault requiring removal.
As you indicated one of your tests was to close off the passenger side vents. Then cooled air came through the drivers side vents. And heating does not have the problem. Doesnât sound like blocked ducts to me.
I think the chiller unit is cooling somewhat, but not enough for both sides.
I would go with a regassing before dismantling the dash in search of rats nests or faults.
You can buy an endoscope from around $10 (depending on length of wire) that will work on a computer, tablet or phone. It has a small camera and light powered by a USB connection. The apps to view the result are generic to the operating system and usually a free download. This is not the kind used to examine the inside of people which are a bit more pricey.
You will need to fasten (ie tape) the business end to something thin and moderately stiff to poke it where you want, going around sharp corners can be a problem especially if the space is narrow. A âsnakeâ as used by electricians and other wire-pullers can be made from various things, the plastic spline for joining T&G flooring is one. An old fishing rod of fibreglass or cane (ferules removed) work too, or in a pinch a piece of dowel.
If you think you might need to look into hidden spaces in your car or house, or anywhere else, it is not a big purchase and can get results that save a great deal of effort in taking things apart to see inside. There is nothing like spending hours disassembling something to turn around and reassemble it because that is not where the item of interest lies.
Hi
The auto mech should be able to tell you in a few mins if the system charge is low.
They will hook up the gauges and see that right away.
Given itâs a 10 yr old car, youâd except the gas would have leaked out over this time.
A low charge will give you a more uneven temperature distribution over your evap. So it is possible to get warm vents in cold setting. Low charge means low evap performance.
All evaps will have a temperature stratification, that is amplified with low charge. It might seem like a sudden onset of issues, but the charge may have got to some tipping point for the evap, leading to a sudden change.
Unlikely the air mix doors have failed, since you are still getting cold air on the LH.
Again, an auto mech ahould be able to measure the temps out of each vent, even air flow, and get an idea of the air-mix door might be the issue.
Even measure voltage if you can get to the actuator easily enough.
You may be able to hear the whirr of the doors opening and closing if you have ignition off, and cycle between full hot and full cold and back again at fan speed of 2 or 3. But not guaranteed youâd be able to hear it working.
And perhaps closing the LH vents just forces that air down the duct to the RHS, so nothing has changed except the re-direction of air.
HVACs are unfortunately complex, and hard to diagnose without seeing it, testing what the temps actually are and felling the flow.
When you say cold, is it really cold, ie. 15/16deg, or is it just below ambient?
Again, unfortunately, youâre best beat is finding a good auto electrician.
My bet is still on a low system charge.
Good luck.
Thank you for your tips.
It seems you have some experience and insight into car air conditioning.
I have tested the air temperature using a very tiny low thermal inertia
thermocouple which responds very quickly and the passenger side vents
measure 9 degrees C, whilst the drivers side measure ambient (no cooling)
which on that particular day was 23 degrees C. Thatâs a big difference.
The air flow is essentially the same through both vents, tested using
a small wind speed meter.
Iâm still struggling to understand how a thermal gradient across the evaporator
can result in chilled air to one side and ambient to the other. But then I am
assuming the air is blown through the evaporator and then through a âsingle ductâ
which at some stage divides into two ducts going to left and right sides
of the cabin. Perhaps the division into two ducts happens much closer to the
evaporator than I imagine, thus the split in air temperatures due to thermal
gradient across the evaporator.
Being deaf as a block of wood, I am totally unable to hear the
whirr of the doors opening and closing. All I can detect is the result
of the change in vent settings.
Syncretic Busted BS suggests checking the cabin air filter, which I have
done and replaced as it was full of grass and all sorts of unidentifiable stuff.
$40 at Repco!!! Ouch!
That filter was the original and thus 8 years olde.
I have purchased a couple of replacement filters on eBay
for only $10 each so the filter will now be regularly replaced.
And Syncretic Busted BS also suggests getting an endoscope which
I think will be a good idea and useful for odd jobs around the place.
About 2 or 3 years ago I noticed a smell coming from the air vents
the moment the blower started up (when first starting the car
each day). The smell vanished after a minute or so running the fan.
The smell reminded me of cow plop or horse exhaust and I had
wondered if somebody had pranked me by putting aforesaid
smelly material into the air intake vents on the bonnet.
Perhaps this could be indicative of rodents trespassing in my
air conducts?
However that smell seems to have gone since replacing the cabin
filter a week ago.
I have seen no other signs of rodent infestation.
Removing the dashboard seems like a lengthy and tedious job
and I donât want to do it myself nor pay for somebody else
to do it either.
The car is now booked in to an air con place next week.
Letâs see how this pans out.
Maybe, maybe not. It could also be that your nose got used to whatever was fermenting in the dirty filter and you didnât notice it anymore. We tend to lose sensitivity to smells after some exposure to them, this is a problem for exposure to danger that is signalled by smell - like leaking cooking/heating gas that naturally has a smell or has odorants added.
Youâre right, the temperature variation is large, but not uncommon with a low charge.
Essentially, at low charge, parts of your evap are not performing. So you can get an evap air off temp off about 5degC in one part, and others may be much higher, maybe 15degC or more.
Once the air comes out the vent, surprisingly, it picks up maybe 4/5degC, so itâs possible to get that 9degC on one side, and 20degC on the other.
I wonder what the centre vent temps are measuring?
Again, Iâm guessing, hard to really say whatâs going on without physically seeing it.
As for the smell, some of the foams used in the system can give a bad smell over years. It essentially gets a bit old and mouldy, hence the smell on start up.
After using your ac a good amount of time, you could try drying it out at the end of your trip by blasting full fan, full heat for a few mins.
Could possibly minimise the smell before you use it next.
Also, some hvac systems have a secret door resetting prompt, a recalibration.
I know for the ford falcons for instance, it was something like holding down the climate control power button and the defrost button at the same time for 5 or so seconds. Not sure if older subis have something similar. Again, perhaps your manual has that info, and your mechanic should certainly know.
It would be interesting to find out if there is a reset/recalibration procedure for the air control doors. One of the control knobs has been acting eratically for awhile now.
The control knobs for the air con and also the audio system are all ârotary encodersâ (as opposed to rotary switches) and the encoder that controls where the air goes, and the audio controllers, have all gone a bit awry the past few years and I suspect maybe Subaru have used cheap and nasty rotary encoders which perhaps are susceptible to ingress of dust and or moisture?
Anyway, the system was re-gassed yesterday and now chilled air emanates from all 4 front vents, so it would seem the problem has been correctly diagnosed and fixed. They added a dye to the gas and I am to return to the place in a few weeks and they will check for leaks via the tell tale dye. I assume it is fluorescent dye, so I should be able to check it myself using a UV torch.
One thing I have noticed is that with the aircon now working again, the yucky smell has returned. That smell has been absent since the aircon croaked and I replaced the cabin filter, but has now returned so Iâm thinking it may be the drainage from the evaporator has become clogged/blocked and thus an accumulation of sweat and body odours condensed by the evaporator have not drained away thus the smell???
All I need to do now is locate the drainage tube and clean it out and see if that helps.
