Oh God... Evap Core?

[mLuMaN83]

So I was doing a bit of digging and as some of you know, I have some AC issues with the whole going warm when it feels like thing as well as recently, some smell. Indi shop tested pressure and said it was OK.

My AC makes this same noise from the inside. Is this a bad Evaporator core? If so, I'm defeated. Parts are expensive and thats an entire weekend worth of work. NOT looking forward to this but I have a feeling that this is my problem... Full time student + no money + my DD = must do it. Let alone the suspension work I must have done. I don't have the tools or time for it so I have to pay labor on it.


http://www.youtube.com/watch?v=nPqA7dLhaVo

[Avetiso]

Don't be intimidated by dash removal. It's not hard.

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[brettbimmer]

It seems odd that the evaporator core would be causing problems unless your AC system is losing refrigerant from a location which isn't obvious under the hood, etc. Have you had the system evacuated and refilled with the proper amount of refrigerant? Depending on who was working on the system, this simple step is sometimes overlooked, and the car is under/overfilled.

Here is a link to the E46 evaporator core. Think of it as a radiator of sorts. "The evaporator allows the refrigerant within the a/c system to lose pressure and cool down, allowing it to transfer that chill to the air coming out of the dash vents." The only thing it can do is hold pressure or leak, as the unit is not electrical. http://www.ecstuning.com/Search/SiteSearch/64119135744/ES177647/

I did have an evap. core leak on a 2-year old Jeep back in the early 2000's, but we exhausted all other possibilities first by testing the system with dye. This is a rarity, not the norm.

IMHO, the video above sounds like the system is low on refrigerant or is over-filled and is freezing up. If you have a suspected leak in the system, they can usually run some neon yellow dye through the system which will help you detect any sort of leaking components. The O-rings in the hard lines are usually the first place to check (near the compressor under the hood, those passing through the firewall, etc.). I had a leak in my E36 this past year, and it turns out that it was caused by some ham-fisted wrenching (by me) when I managed to press a bit too hard on one of the hard lines running to the firewall, thus causing a slight crack in a weld that caused the refrigerant to leak out (as was evidenced by the dye that my mechanic had put in the system). While I was in there, I replaced the drier and another hard line, along with the small green o-rings on the end of each hard line. A few months later, I preventatively replaced the AC compressor, but the car has 250,000 miles on it, and my compressor sounded like a cat inside a washing machine when running, and I was losing performance in the system as it was unable to pressurize the system like it used to back when the system was a bit newer.

What I have learned throughout my AC work is that the system is relatively simple once you understand how it works. If you Google up some basic car AC diagrams, you may find them helpful.

I hope this is helpful. Let us know the full history on your AC (including any work done), along with the exact symptoms of the problem. Also, how many miles are on your car? Hopefully we can help you pinpoint the problem before you tear into the system.

[mLuMaN83]

I think what I need to do is take it into BMW and have a proper diag done. It will all the sudden go warm when I am driving. If I shut the car off for awhile, it's ice cold again but then when it feels like, goes luke warm. I took it in last year to an indie shop and they tested the pressure and said it was ok. I also filled with refrigerant. I then replaced the AC Control Unit and that did not fix the problem either. Sometimes the AC will work fine for even days and then all the sudden, warm. It acts as if the flaps change because it is still blowing cold air inside the dash in some places. It also has a bit of a smell lately. Almost like a smell of refrigerant but this smell is only on start up and fades after a few minutes that the system is running. 153k on the clock, original compressor.

I need a proper BMW Diag...

[Smolck]

what you need to do is hook it to a manifold gauge set so you can see what the high side and low side are doing at the same time. Armed with that knowledge, you can then proceed with further steps. To me, it almost sounds like your system is OVER filled which would allow the high pressure cutoff to come on and stop the compressor from doing its job. If that happened, you would get hot air. The fact that you say when you let it sit, it blows cold again further supports my theory because when left to sit, the pressure will come back down again.

If you had a leak in the evap core, your a/c would lose ALL it's refrigerant and would NEVER blow cold. I doubt it is that.

[brettbimmer]

what you need to do is hook it to a manifold gauge set so you can see what the high side and low side are doing at the same time. Armed with that knowledge, you can then proceed with further steps. To me, it almost sounds like your system is OVER filled which would allow the high pressure cutoff to come on and stop the compressor from doing its job. If that happened, you would get hot air. The fact that you say when you let it sit, it blows cold again further supports my theory because when left to sit, the pressure will come back down again.

If you had a leak in the evap core, your a/c would lose ALL it's refrigerant and would NEVER blow cold. I doubt it is that.

X2.

I am guessing that it usually stops blowing cold on the really warm days when you need it most? If so, that supports the overfilled hypothesis too, as the system is usually working harder in warmer temps.