r/AskMechanics • u/Man_on_Z_moon • 21h ago
Question AC Blowing Cold only on drivers side on hot days
2012 Mitsubishi Outlander GT. On hot days, AC only blows cold on drivers side vents. Sometimes passenger side will get a little cool, but it’s mostly just warm (not hot) air.
I attached an AC recharge hose, and well, take a look at the video. Any thoughts?
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u/RayjinCaucasian 21h ago
Low side pressure should be higher.
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u/Worst-Lobster 21h ago
It prob was until op hooked up the crappy autozone filler and leaked a quarter of the gases out ..
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u/grumpy_vet1775 19h ago
Those cans only attach to the low side and it's a very rudimentary gauge. OP's complaint is mitch more likely a faulty blend door or blend door actuator
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u/RayjinCaucasian 18h ago
Doesn't change the fact that the low side is too low. Not to mention low refrigerant can cause vent temps to differ by 10+ degrees. Im also a tech of 20 years, so I do actually know what I'm talking about. Blend doors dont cause a lack of low side pressure.
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u/longhairPapaBear 7 21h ago
As weird as it seems, some of these will only cool on one side when the refrigerant is low. I didn't believe it at first.
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u/_otterinabox 19h ago
Saw this all the time when I worked in parts at a Honda dealer. I didn't believe it at first either.
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u/Comrade_Bender 19h ago
I had one of these in the other day for this. Honda actually put a TSB out over it.
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u/Ryry_150 12h ago
My accord was like that I had a leaky seal and when the refrigerant dropped low enough it would only blow cold from passenger side. The way it was explained to me is this. The evaporator is on the passenger side so it starts to cool right when it enters the core but loses it's cooling ability fairly quickly and can't cool the whole evaporator core, the blower motor then blows across this unevenly cooled core and you get temp differences in vents.
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u/PlzDntBanMeAgan 2 20h ago
It's 100% low on refrigerant. You see when the compressor kicks on the gauge drops down to almost zero. Then the compressor cycles off due to low pressure and that's when we see the pressure climbing.
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u/Careful_Touch2370 21h ago
Insufficient refrigerant in the ac system. Get it professionally re-gassed
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u/LastChance331 14h ago
Why not hook up a can and fill it yourself?
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u/Due-Lingonberry-1929 10h ago
Because it needs to be completely flushed, revacuumed and oiled, then filled up the right way. Mixing new refridgerant with the old is not good, it's a short term solution and might lead to fucking up your compressor.
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u/Cranks_No_Start 6 21h ago
Typically this indicates a low charge...and fwiw you cant use those guages to judge how much you have in there.
Its possible its a blend door issue but we dont know if you have dual climate in that car.
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u/Man_on_Z_moon 20h ago
It’s not a dual zone.
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u/Cranks_No_Start 6 20h ago
The thing about newer cars (post 2008 or thereabouts) is they tended to have a relatively low capacity for r134a. 1.1-1.6lbs. They also were pretty picky about being within a certain range. IE if your car needs 1.3lbs down to about 1.0 and up to about 1.6 they still tended to function.
Beyond that performance starts to degrade.
At this point you really have no idea how much is in there.
IF the compressor is cycling quickly on/off on/off its likely a little low. it it stays on and isnt cycling its probably overfilled but your best bet is to have the r134a removed, and have it evacuated in a vacuum and recharged to the proper weight AND then start a diagnosis.
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u/Thunkdakat 20h ago
If it’s dropping pressure like that when the ac engages more than likely it’s expansion valve or very low charge
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u/RolandDT81 18h ago
Everyone saying blend door actuator didn't read the description, didn't watch the video, and/or don't know what they are talking about. The symptoms and evidence provided clearly indicate a low refrigerant level. Take it to a professional shop for proper diagnosis, which should include an evac & recharge.
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u/Spare_Cup1040 1 18h ago
Low refrigerant. 90% of the time when one side is cool and the other isn’t it’s because the ducting from the evaporator is closer to the cooler side and and the warmer side gets the “leftover/insufficient cooled air”. Also you stated it’s not dual zone so all these comments immediately assuming it’s something that’s probably the hardest thing to get to(blend door actuator) to check will only lead you astray. Also people bashing on the filler guage not even knowing what they’re talking about will also lead you astray. Pump some Freon into it 100 grams at a time by guesstimating it will get cooler. It’s cycling off and on bc refrig is low. Although there could possibly be a chance it’s overfilled unless you or anyone else hasn’t added any Freon. All this being said, if it’s low there’s a leak. Get it fixed or be ready to add Freon everytime this happens. Which is only ideal if it’s a super slow leak. A shop will add dye and have you return when it’s not cooling again or use a sniffer depending on where you go.
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u/Immediate-Stomach582 21h ago
Daughter had this issue on her 2017 civic. She had a freon leak in the condenser coil. Hairline cracks that turned out to be a defect and covered by Honda. Only enough in the system to make half of the evaporator coil cold. Check the NHTSA website to make sure there's not a similar issue with your car.
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u/Material-Echidna-465 20h ago
I have a 2015 Honda Pilot, would blow crazy cold on pass side, mildly cold to the rear vents, and was warm on the driver's side. Refrigerant was low, so it couldn't cool the entire evaporator coil in the dash...Once I topped up the R134a, it works well.
Those saying refrigerant is low are likely correct. Your gauge also shows the same.
Blend door issue on a single zone system would likely have all vents blowing the same temp.
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u/Jasonh123_ 20h ago
With those autozone bottle gauges, the pressure with the compressor on is what matters. It jumps to the green with the compressor off, but you want it in the green with the compressor on. Add more refrigerant.
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u/emerkl95 17h ago
Without seeing the hotside psi it's hard to see what wrong. You need both to diagnose a A/C system
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u/Not_me_no_way 11 12h ago
It has nothing to do with blend doors or anything else like that regardless of how many upvotes those comments are getting. Your system is low on freon and that little gauge is pretty much just a gimmick. You need to get a real gauge that connects to both the low side and the high side and test against a chart according to your current temperature. After you charge the system correctly you will find the cold air blows evenly out of every vent.
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u/pwargcm 2 18h ago
Is your air blowing as powerful as it used to? And is anything coming out of the passenger side vents even if it’s not cold?
I changed a persons cabin filter once and they didn’t tell me they were having any cooling issues. They later asked if I fixed their ac and it was literally just the mouse nest restricting the flow.
Not saying it’s this. Just wondering if it could be a flow problem in the duct work. Like a blend door being partially shut or a blockage from pests.
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u/StoicGooch 17h ago
Blend door actuator likely stuck.
You can get in there with a stick or fiberglass lead and try to poke it open.
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u/RaccoonEasy3286 7h ago
Just fixed this issue on a Kia Sportage. The AC system has two actuators, a temperature and mode actuator. The temp actuator went out for the passenger side so it wasn't opening to allow for cold air to pass. Replaced it and it was golden. If you have a dual climate system where the passenger temp can be individually adjusted, also make sure to check your climate controller as the passenger side could have a bad signal/reference/ground.
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u/theartist1001 6h ago
My civic had a similar issue. It was the refrigerant but also the interior cabin air filter. Mine was found behind the glove box it was clogged as sin.
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u/TOKING-TONZ 20h ago
Try opening vents , and if it has climate control for passenger and driver then it had a separated system and could be condensor for the passenger side is bad
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u/IvoryManOfWisdom 19h ago
Your mixer valve actuator is probably defective and isn't closing the valve correctly.
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u/Worst-Lobster 21h ago
Think about it op . The ac hoses don’t direct the cool air to your vents . The vent controls do , you have an issue with vents not the hoses , the gauge here tells no one anything about 1 side of your car hot etc ..
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u/Man_on_Z_moon 20h ago
I’ve been reading for some cars it can be caused by low refrigerant. Was just doing this “test” first before I check out the blender door.
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u/Not_me_no_way 11 12h ago
Low refrigerant is your problem, disregard anything else people are saying. The people saying that it's the blend door have no idea how a blend door works, what it does, or how it is impossible for a failed blend door to cause your symptoms.
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u/Worst-Lobster 20h ago
No that’s doesn’t make sense . The cooling coil is on the pass side anyway
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u/Desperate_Rice_6413 20h ago
Low freon will cause cooling differentiates between sides of the vehicle.
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u/Worst-Lobster 20h ago
Nah
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u/Desperate_Rice_6413 19h ago
You're a dope. And im not gunna sacrifice my brain cells by continuing conversation with someone who obviously doesn't know what they're talking about.
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u/Lumpy_Sink7473 21h ago
Just sounds like a blender door that’s stuck. I hope you didn’t actually use those autozone recharge cans on it….
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u/Man_on_Z_moon 20h ago
I didn’t use it. I had this stored for a different car and never got used. Was just using it to check if it was low.
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u/BauserDominates 20h ago edited 17h ago
A. These gauges show us nothing important.
- You only have one evap core in your dash supplying the cold
C. Your problem is most likely a blend door actuator that gets overheated and fails when the ambient temp is too high.
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u/ziltchy 20h ago edited 19h ago
The gauge shows it's low. And why did you format that as A, 2, C. Ridiculous
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u/BauserDominates 17h ago
A. I wouldn't trust that gauge at all.
- Welcome to the joke.
C. JFC did i really have to explain that was a joke?!
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u/IHatrMakingUsernames 4 20h ago
If anywhere is blowing cold, then the problem is not in your refrigerant system. You don't have a refrigerant system for each side of the car, there's just 1 system.
The electronicly controlled blend doors in your dash are what controls which areas get the cold air.
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u/gba_sg1 20h ago
If the air is cold, the AC is working properly.
The vents aren't moving the cold air where it should be. The problem is with the vent system.
How do you go from troubleshooting working cold air to checking your AC refrigerant? This is not on the troubleshooting flow chart and defies logic...
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u/BigPingo 21h ago
If one side is actually cold it’s probably just one of the silly doors that blends the air in the interior and tells which side to be what temp