[SP3333D]

A few days ago my AC appeared to suddenly stop working. I am relatively familiar with the common components that could fail and have searched through the forums to try and find a duplicate scenario. The problem that I have is that the next morning, I got in my car and the AC worked...

I have found that ~75 degrees is the tipping point. If the ambient temperature is below 75, then my AC is bone chilling cold. If the ambient temperature is above 75, then my AC blows hot air...

Any thoughts on what is causing this? Is there a thermometer or sensor somewhere that might have failed to cause this? I am scheduled to see the dealer tomorrow for an oil change and will have them look at it, but I want to figure it out as much as possible before I go in.

[thomas88162]

You may have a small leak, I would get your refrigerant levels checked by a qualified shop.

[SP3333D]

Originally Posted by thomas88162

You may have a small leak, I would get your refrigerant levels checked by a qualified shop.

Well, the simple answer is that it was 1/2 pound low in a 1.3 pound system... I am surprised that it blew cold air at all, I thought for sure that it should be warm all the time if it was low enough to be effected like that.

6/6/14 - Hasn't leaked since being cycled and the problem was not fixed, it was just cool enough outside when it was cycled to be unable to duplicate the problem. Has everyone baffled now.

[SP3333D]

So a little follow up. Had the system cycled, ran cool for a day (granted that it was under 75 degrees out that day) now it is back to doing what it was doing. Had 2 shops verify that it still has the right amount of R134 in it and there are no leaks... Headed into the dealership Monday to try and figure it out...

[ken1137]

Keep us updated. I had the same problem...one BMW dealer said "cannot duplicate customer concerns". In all fairness this was their response to every concern The 2nd dealer recharged my AC and all is well again, but they could not find any leaks or problems either.

[thegamemodo9]

Temperature sensor? Your car thinks it's certain temperature and only blows cold air depending on that sensor reading.

[El Cheapo Loco]

Subscribed. Having the same issue.

[SP3333D]

Originally Posted by thegamemodo9

Temperature sensor? Your car thinks it's certain temperature and only blows cold air depending on that sensor reading.

This is where I am putting my money. I haven't seen any diagrams on this setup, but I know that a lot of systems have a sensor on the compressor that fails and causes the AC to stop all together. It is the fact that it still works sometimes and is not a total failure that seems to have everyone baffled.

[Manoah]

lol. mine doesnt work either. even after having it checked out and recharged.

[falconey]

Maybe a dumb suggestion/question, but you do have the dial on the center stack moved to the blue/cold side correct? If not that will affect temps from the a/c.

[thomas88162]

You may even look into the valve which modulates the compressor. They are another electronic addition to the variable displacement compressor.

[SP3333D]

Originally Posted by falconey

Maybe a dumb suggestion/question, but you do have the dial on the center stack moved to the blue/cold side correct? If not that will affect temps from the a/c.

lol, This is a valid point, but I would hope that none of us here are that much of a novice... My problem seems to be ambient temperature related, not based on flipping a switch. Who knows, I haven't figured it out yet...

Originally Posted by thomas88162

You may even look into the valve which modulates the compressor. They are another electronic addition to the variable displacement compressor.

I had given this some thought too, I understand that there may even be a thermostat of sort on there that could be shutting it down. I am trying to get some spec sheets and the applicable service bulletins to verify.

[NEFARIOUS]

Originally Posted by falconey

Maybe a dumb suggestion/question, but you do have the dial on the center stack moved to the blue/cold side correct? If not that will affect temps from the a/c.

Switching over from a line of non-Euro cars, this threw me off transitioning from AC to heater... "How the hell is it blowing rather cool air when I have the frickin' heat turned all the way up?"

[SP3333D]

Soooooooo, after 4 hours of diagnostic, the dealer determined that the compressor is shot, but still barely functional. They explained that it appears to be overheating due to some type of failure and it is shutting down when it gets too hot. The car could keep it cool enough on colder days, but not on hotter days, so the AC became ambient temperature dependent.

I ordered a new Denso compressor yesterday from Amazon for $340 with next day shipping and they got it this morning. The dealer quoted $1,440 for the BMW part plus 3.7 hours of labor. The quote was for roughly $1800 I will update this with whether or not that that did the trick once I get it back(Hopefully tomorrow!!)

[Davey303]

Another thing to think about, is the color of your dash and whether or not you're using a sun shade. I found, with my black interior, that the dash would get way hot and when the AC was on, it was blowing warm air. Turns out, this is due to the dash "absorbing" all of the cool air or warming the air on the way out. After the dash would cool down, so would the air coming out of the vents. I've started putting a sun shade in whenever I park and it's made a world of difference.

Also, your A/C can only do so much, I believe they say it can only cool the ambient air down by 20-30*F. So if it's 100 degrees out, you may very well only be getting 80* temps out of your vents because that's all the A/C unit can do.

Just a thought/tip!

[ERIC212NYC]

Subscribed, my 2009 E90 just started doing this past weekend. I am taking it to my local shop to get it checked out.

[El Cheapo Loco]

Originally Posted by SP3333D

Soooooooo, after 4 hours of diagnostic, the dealer determined that the compressor is shot, but still barely functional. They explained that it appears to be overheating due to some type of failure and it is shutting down when it gets too hot. The car could keep it cool enough on colder days, but not on hotter days, so the AC became ambient temperature dependent.

I ordered a new Denso compressor yesterday from Amazon for $340 with next day shipping and they got it this morning. The dealer quoted $1,440 for the BMW part plus 3.7 hours of labor. The quote was for roughly $1800 I will update this with whether or not that that did the trick once I get it back(Hopefully tomorrow!!)

Please post link to said compressor and let us know if it did or did not correct the issue. Much appreciated.

[e92_enthusiast_1]

bump to remove spam from top

[SP3333D]

Originally Posted by elcheapoloco

Please post link to said compressor and let us know if it did or did not correct the issue. Much appreciated.

there are apparently 2 compressors to choose from. one went up to 03/2007 and the other is from 03/2007. my car was actually built in 03/2007, so the dealer directed me to use the second unit, from 03/2007.

this should take you to the one that I bought. (I paid $332 +$8 overnight shipping)
http://www.amazon.com/dp/B004SG323E/..._6X9Ltb07ZPAT4

this model number ends in 1529, I believe the other compressor was the same model number, but ends in 1532.

they got the compressor this morning, 18 hours from ordering to delivery (I love amazon), but ended up having to order new bolts and have to wait until Thursday to get it put back together. I will update as soon as I get it back!

[SP3333D]

Originally Posted by Davey303

Another thing to think about, is the color of your dash and whether or not you're using a sun shade. I found, with my black interior, that the dash would get way hot and when the AC was on, it was blowing warm air. Turns out, this is due to the dash "absorbing" all of the cool air or warming the air on the way out. After the dash would cool down, so would the air coming out of the vents. I've started putting a sun shade in whenever I park and it's made a world of difference.

Also, your A/C can only do so much, I believe they say it can only cool the ambient air down by 20-30*F. So if it's 100 degrees out, you may very well only be getting 80* temps out of your vents because that's all the A/C unit can do.

Just a thought/tip!

that is definitely a good point and a consideration. in my case, the windows all have a dark tint and the windshield has a moderate tint on it. my cabin is rarely 15 degrees or more above ambient.

[SpaceyGray]

Originally Posted by Davey303

Another thing to think about, is the color of your dash and whether or not you're using a sun shade. I found, with my black interior, that the dash would get way hot and when the AC was on, it was blowing warm air. Turns out, this is due to the dash "absorbing" all of the cool air or warming the air on the way out. After the dash would cool down, so would the air coming out of the vents. I've started putting a sun shade in whenever I park and it's made a world of difference.

Also, your A/C can only do so much, I believe they say it can only cool the ambient air down by 20-30*F. So if it's 100 degrees out, you may very well only be getting 80* temps out of your vents because that's all the A/C unit can do.

Just a thought/tip!

Cooled air exiting the vents will be in the 40 degree range, not the 80's however, the max overall drop in cabin temperature is in the 20's. Same holds true for home A/C systems.

[SP3333D]

Day 4 at the dealer, got all of the necessary parts in and they started taking it apart yesterday and broke the aluminum bolts holding the part on. They got new bolts this morning and went to to finish the job, spent all day extracting the old bolts and then finishing the install. Then as they were putting it back together, the top radiator hose broke... Now we have wait until tomorrow for a new one to come in and finish the installation...