AC blows warm air through one vent, even with new compressor

[herwawan]

Hey, it's this time of the year with super hot weather and the AC decides not to work properly.

Symptoms are:
- not very cold air coming from all vents
- warm air coming from one of them specifically (center vent, the left side close to the driver).

I decided to go for a diagnostic and recharge at my favorite shop in LA. There, they checked the amount of freon in the system - from the 1.63lbs spec, I had 1.10lbs of freon so it was low by 0.53lbs. They proceeded with the recharge but it didn't fix the issue.

They looked at the AC compressor, which seemed to be the culprit: it was clearly noisy every time it was engaged. They replaced it, confident it would fix it. After a test drive, everything looked good, they measured 40F at the vents when setting at 59F and they gave me the car back.

After 10 minutes of driving on the freeway, the vent that was blowing warm air was back at doing exactly that and the other vents were not that cold anymore. I got a bit mad, brought the car back and they are now looking at it again.

The main reason I'm mad is because of the amount of money I dropped into this repair (I will go on a long road trip soon and I need the AC to be 100% functional) for something that, quite literally, didn't change a thing. I don't blame the shop yet - they've handled it very well so far despite the situation and I'm looking forward to seeing what they find.

But in the meantime, I wonder if any of you didn't run into a similar issue and successfully figured out a solution. Maybe that could be some tips I can send their way that will save me some lengthy diagnostic...

[Rkymtnrider]

Did you replace the drier too?

[duracellttu]

Did you replace the AC line o-ring seals that go into the compressor? Sounds like the Freon is leaking from someplace. Try doing a UV light/dye test to try and track it down. If that isn’t it, you could need a new evaporator.

[Icecream]

The main reason I'm mad is because of the amount of money I dropped into this repair

Welcome to the club lol.
Anytime you are low on freon, you get warm air from the passenger center vent first, not the drivers side as you stated. That is odd. Can you confirm that is in fact what is happening? I wouldn't freak out yet, shop probably missed a leak. I couldn't imagine A/C not working right now, it is brutally hot here and for some reason the e46 gets unusually hot in the sun and turns into a furnace - I would rather ride a bike and sip on a hot tea than sit in an e46 with no AC haha.

[herwawan]

Did you replace the drier too?

They meant to replace it initially, yes. Unfortunately, they didn't have enough time to replace the receiver drier as they needed to get the front bumper off. Since the plan was for me to drive the car back at the end of the day... well, I ended up having to leave it there anyways now so we'll see what they decide.

From my understanding, the role of the dryer is to prevent moisture in the cabin, correct? Could there be a link to the issue?

Did you replace the AC line o-ring seals that go into the compressor? Sounds like the Freon is leaking from someplace. Try doing a UV light/dye test to try and track it down. If that isn’t it, you could need a new evaporator.

I don't know if they did. Good one - I'll ask.

The interesting part about the leak idea: after filling up the circuit the first time with the old compressor, they did check after the test run the level and it didn't change. Which may indicate no leaks? I'm really not an expert in AC and after reading a lot about it tonight I realize how both simple and super complex it is so I'm open to any piece of knowledge you can throw at me haha

Welcome to the club lol.
Anytime you are low on freon, you get warm air from the passenger center vent first, not the drivers side as you stated. That is odd. Can you confirm that is in fact what is happening? I wouldn't freak out yet, shop probably missed a leak. I couldn't imagine A/C not working right now, it is brutally hot here and for some reason the e46 gets unusually hot in the sun and turns into a furnace - I would rather ride a bike and sip on a hot tea than sit in an e46 with no AC haha.

I'm 100% positive: the warm air comes from the left side of the central vent, driver side.

Hahaha I feel you. It is hot but I'm glad it's happening now though, it's a good stress test on the repair.

[RoyalFlushness]

Mine does the same lol. Havent tried to fix it yet.. warm air comes from both passenger side vents and cold air comes from drivers vents.

[Cubieman]

From my understanding, the role of the dryer is to prevent moisture in the cabin, correct? Could there be a link to the issue?

The role of the drier is to keep moisture out of the AC system itself. It is generally something one wants replaced when the system is opened up for service.

[herwawan]

The role of the drier is to keep moisture out of the AC system itself. It is generally something one wants replaced when the system is opened up for service.

Roger that. Well they will replace it today now that they have all the time in the world haha I'll report back if that leads to any improvement.

[duracellttu]

The role of the drier is to keep moisture out of the AC system itself. It is generally something one wants replaced when the system is opened up for service.

Not sure I agree with this. When you get the system professionally flushed you are taking out any moisture/humidity in the system. If there was sooo much moisture that it caused condensation and water was left in the system, then yes that would be an issue. I don’t see how that could happen over the course of a single day during a compressor swap.

[yhp2009]

Not sure I agree with this. When you get the system professionally flushed you are taking out any moisture/humidity in the system. If there was sooo much moisture that it caused condensation and water was left in the system, then yes that would be an issue. I don’t see how that could happen over the course of a single day during a compressor swap.

From what I understand the drier has a usability expiration kind of like a filter. So its not a bad idea to replace it either way.
As for the moisture getting into the system, I always thought it was an instantaneous event. Since the AC system is a closed system, as soon as its opened, all the moisture in the atmosphere goes into it. When its closed up again it either needs to be vacuumed out or "filtered" out by the drier.

[PetrolM3]

Just went through this same ordeal. A/C stopped blowing cold (starting with passenger vent then all). Had a noisy compressor and a leak on the condenser connection. Due to mileage and cost to refill, I decided to replace compressor, condenser (gets beat up by stones and can end up leaking) as well as the drier (needs to be replaced every time you open the system), expansion valve, schrader valves and all o-rings. The shop pressure tested the system with nitrogen (which also soaks up all the moisture) and only once they were sure there was no leak, they flushed it (I believe they call this 'vacuum flush') and then filled it to spec including the right amount and type of oil for the compressor. Working great since then. Got all my parts at FCP euro so I never have to pay for them again in case of issues in the future.

Sounds like you still have a leak and I’m surprised the shop didn’t pressure test the system before they determined it was your compressor and before they recharged it. If they missed a leak, they should at a minimum recharge it for free once the leak is fixed.

Good luck!

[Cubieman]

Yeah, I should rephrase that I suppose. I don't think its common to replace the drier each and every time the system is opened. But moisture is introduced when the system is opened and if the drier is original to the car its probably a good idea to replace it.

[Rkymtnrider]

Just went through this same ordeal. A/C stopped blowing cold (starting with passenger vent then all). Had a noisy compressor and a leak on the condenser connection. Due to mileage and cost to refill, I decided to replace compressor, condenser (gets beat up by stones and can end up leaking) as well as the drier (needs to be replaced every time you open the system), expansion valve, schrader valves and all o-rings. The shop pressure tested the system with nitrogen (which also soaks up all the moisture) and only once they were sure there was no leak, they flushed it (I believe they call this 'vacuum flush') and then filled it to spec including the right amount and type of oil for the compressor. Working great since then. Got all my parts at FCP euro so I never have to pay for them again in case of issues in the future.

Sounds like you still have a leak and I’m surprised the shop didn’t pressure test the system before they determined it was your compressor and before they recharged it. If they missed a leak, they should at a minimum recharge it for free once the leak is fixed.

Good luck!

Which compressor did you go with? OE bmw or oem manufacturer?

[clawhamm3r]

Yeah, I should rephrase that I suppose. I don't think its common to replace the drier each and every time the system is opened. But moisture is introduced when the system is opened and if the drier is original to the car its probably a good idea to replace it.

It's one of those "supposed" to things. Can you reuse the copper crush washer on your oil drain bolt? Yes. Will it leak? Maybe. But if it does do you want to drain the system/oil to fix the problem? Probably not. Esp when it's $25 and like 10-15 minutes to swap I'd rather just do it. And like you said if it's old definitely do it. If you just replaced it and have to open the system back up to chase the problem further...start there with opening the system and tape it off lol.

OP mine has been leaking for years and when it gets low enough it blows warm on the passenger sides. I've read for years that the hissing behind the dash and the other symptoms was the orings on the expansion valve. I recharged it every 1.5-2 years as my fix lol. Finally decided to do it last month, replaced the valve because it was another $30 part while I was in there. Bought the ECS O-ring kit which was missing o-rings and some were wrong. I need to post an FYI on here about that.

Anyway, I replaced the valve, drier, and all orings in the system after having it discharged. Took it back to get it recharged and it's been colder than it's ever been...let's see how long it lasts.

[TropicalM3]

You can also check the mixer valve, if it is stock in the position where it allows hot water to flow thru the blower box you all always hot air in the car. It happened to me and when i changed that the A/C was great again.