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Discussion Starter #1
I looked for info on this on the site, but didn't see any, so I thought I'd share my experience in case it helps anyone.

On a trip down to visit my mom about 600 miles away (south) in hot weather, the cabin became gradually warmer. I turned up the air and HEARD it blowing strong, but little or no air was coming out, anywhere. I researched and tried stuff.

I'll spare you all my machinations. Bottom line was, the A/C coil was apparently freezing up and blocking the airflow. Rather than turn off the car and let it thaw, I figured out that if you just turn off the compressor, as the ice melts, the air continues its meager flow through (or around) the ice, and as the ice melts, the airflow increases. The air is still reasonably cool because the ice is cooling it. After 10 or 15 minutes of this, the air was flowing strong and I turned the compressor back on. All good, everyone comfortable.

FWIW, I run my climate control on Auto, with the "automatic programs" set to medium, and the temp at one or two blue bars, and the cabin temp dial at around 70 degF.

The $64,000 question is, does anyone know how to KEEP this from happing in the first place? None of the other E60's I've experienced had that issue. My brother had an '07 550i, then a 2010 535i, I had an 08 550i M Sport (poor man's M5, basically) , and my mom had a 2010 535i wagon, none of which never had that issue. Something specific to the M5? Or A/C on the '06 is sub-par? I do notice there seems to be a LOT of condensation that drips out of it.
 

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Bring it to a shop and have them measure your hi and low side. They can also do an evac and fill so you have the proper refrigerant level. This is not something you should try yourself since you need the right tools and knowledge. No offense, but if you had them you’d probably not have asked.

If you’re lucky you may simply have overcharged the R134a. that can cause the freezing of the evap coil which seems to be what you’re describing. You made no mention about any attempts to add refrigerant, I’m presuming you did since that’s what most ppl do. An underfilled system generally doesn’t freeze, unless there’s an issue with the TXV. That is going to be very costly since it is REALLY hard to get to.

When it’s humid like it has been you’re going to see a lot of water draining from the evap coil, that’s exactly what is supposed to happen.
 

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Discussion Starter #3
FYI, I've not tried to maintain my A/C at all. I have a LOT of experience working on my BMWs in my driveway, meaning, I know what I shouldn't try to do. I'm not a professional mechanic and I have minimal specialty tools. Presses for ball joints, yada yada, that kind of thing, but nothing deep. Throttle actuators, timing chain guides, suspension rebuilds, and that sort of thing I've done successfully multiple times on various I6, V8, and V12...I'm totally new to the S85, though. Been a dream of mine to own (work on constantly) one.

My comment regarding dripping condensation is based on my experience with tons of other BMWs in this climate, including a few E60's as I mentioned. This one appears to be much more. I start the car outside a hotel portico, and leave a trail all the way to a parking place. I've never seen it to that degree.

Anyway, I'll set up an appointment with my indy and see what he comes up with. He's always great.

Thanks for the info!
 

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The refrigerant will leak out over time. It happens on all cars. Moisture then also seeps in. When enough moisture was introduced to the system that the desiccant can’t absorb it, and it freezes in the evaporator coil. Moisture also tends to get in when you try to top off the system with those can kits and ppl not purging the line.

Ask the shop to do an evac test and if the are good or specifically asked can do the vacuum test for 30 min or longer. This should let any water that is in your system boil off. If your car passes the leak test only then would he refill it with the correct amount of R134a and oil. You never fill a system that will not hold vacuum,that’s just wasting refrigerant and your money. There is nothing special about doing and evac and fill for a BMW or M5.

However for the E60, I hope for your sake it is not the TxV. It is on the inside of the firewall. There is NO access to it, you have to remove the whole dash and evap case to get to it. I’ve done this before and it is a solid day’s worth of work. It will cost you more than the car is worth when all is said and done.
 

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Discussion Starter #5
Let’s hope it’s not a dash removal. Did that to replace a blower motor in my 2000 740i. Big pain.
As for cost, as far as I’m concerned, the minute cost of ownership becomes a consideration, a used M5 becomes NOT a consideration. To me it’s a special beast. I’ll work for it.
 

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Discussion Starter #8
Sorry, what do you mean by ista/inpa? I have a cheap scan tool for the standard obdii stuff. That’s it.

I bought the car last February with 52k on the clock. Was gone over by my Indy right after I got. No codes, no leaks, no nothing. One owner, garaged, driven on the weekends, and very very well maintained. As nice an 06 anything as he’d ever seen. It’s still under 54k now. Not that it’s an indicator of anything, but that was the status not too long ago.
The original owner was great, but he did have A/S tires on it, so he obviously wasn’t a spirited driver. lol
Squishiest wimpiest damn tires I ever drove on a car like this. That was the first thing I changed.
 

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For OP it’s important to check the fundamentals first. High and low side pressure. That can tell the tech if it’s over or under charged. The evac test is needed to ensure your system has no leaks and hopefully boil off any moisture. Once that’s done the tech should refill it to the proper weight and oil charge. Then you can see if it keeps freezing. Most likely if all this is done then this will eliminate the possibility of over/under charging. Also the water freezing in the evaporator and icing up. This won’t be wasted money. The car is 10+ yrs old.

if it still does this then there’s more troubleshooting which could lead to this sensor or other stuff. For AC systems you have to make sure the charge in the system is correct first, and 10 yr old cars will likely be under charged. Of course if there are codes that say the sensor is bad then maybe that’s all you need to do. It’s usually not that easy though.
 

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Let us know what he says. I can’t see a pressure check, evac and fill costing more that 300-400, but actually never have anyone other than me touch my car. It’s worth it to have him do the vacuum test for 30 min or longer, you’re paying for extra fish time. Some of the cheaper shops skimp on this cause they want to turn over the cars faster, but the time is required to let the moisture boil off.
FWIW, I leave my machine on for 1hr and the machine default is 40 min.
 

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Discussion Starter #12
Thanks, good to know. I’ve used this one-man shop for 15 years. Great guy. There’s a collision shop next to him who charges me out the nose for alignments but their work is noticeably better than the chain places so I pay. They actually maintain their rack and put weight in the cars when they align them. It’s amazing how many shops align BMWs the same way as Chevies. Regarding the AC, worst case scenario I’ll have him fill it with Jack Daniel’s and open the windows. :p
 

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Just to jump in because I did A/C work for years on cars. BMW systems are pretty good overall, EVAC and proper charge is a great first step. With that said the system should shut down before it freezes. If I am not mistaken BMW uses a variable displacement compressor, a TXV and a low pressure cut out switch. The first two would not respond well to a low charge the last should. Modern cars have a very small reserve of refrigerant and as already stated all systems leak.

Never, ever, ever put any kind of sealer or seal softener into an A/C system unless you want to write it off.

While the Auto system should handle it putting the system air on recirc will reduce the moisture after the cabin is cooled off. If your auto system is not doing this that may be the reason for all of the condensate drain and the freezing?
 

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OP.
This happens to me maybe 3 or 4 times a year on long hour plus drives.
I live in S. Florida where we run AC year round.
Like you, I just turn the AC off leaving the blower on for a few minutes to thaw.
Never really worried about it as just leaving the fan on for 5 minutes was a lot less expensive than chasing the problem, and seemed to yield a satisfactory and affordable end result.
I just chalked it up to being in super humid Miami.
With this said, subscribed...
BTW - Back in college my first year on campus I had an "illegal" window ac (I was super popular for a few hours a day) that did the same thing.
 

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Also... I never run on recirculate (always fresh air for me) so add that to my list of reasons ($$$) for not chasing the issue.
 

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It’s hard for anyone to diagnose these things by reading a few sentences. Especially if the person is not experienced in AC systems.
Hard to know what is icing up, if it’s just condensate backed up in the drain that is icing or the evap coil icing up on the inside, failed sensors, etc.
 

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Discussion Starter #17
Just got it back. He check hi and lo side pressure and put it on a two hour vacuum. No leaks. Said he used dye and found none.
Was low on refrigerant. All good now.
 
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