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Nicoromag 01-24-2013 08:49 AM

AC wacky behavior
Hello to all members, this is my first day and post as a new beemer owner. I just purchased a 2004 BMW 745i and at first noticed the AC blowing warmer than it is programmed on screen on drivers' side but would blow cold as programmed in passenger side while being set for the same temperature in both sides, in addition, the AC panel lights would blink randomly on and off for a short period of time and get back to steady on. Last night the AC panel light wouldn't turn on at all, but the AC itself wouldn't stop blowing heat at 127f (which i had to block the vents and open windows in order to not pass out..) I tried pressing the off AC button and then turning the car off and start it back on to see if it would restart the computer but no luck in both cases. Curiously enough, after a couple of hours of the car being off the AC came back to its original issue (incorrect dual temperature)
Please help!

hd750Li 01-24-2013 01:33 PM

There's probably an issue with the AC regulator unit which is underneath the glove box. Very easy to replace. OEM brand new cost about $180 part # 64116934390. You probably could find a cheaper used one on eBay.

Nicoromag 01-24-2013 02:14 PM

Thank you for the reply! What worries me is the little "lights show" of the panel and the fact of shutting down of the system while still working, would that be also related to the regulator? doesnt the reg just controls the temperature? Climate panel is ruled out?

hd750Li 01-24-2013 04:17 PM

No, not entirely ruled out yet. As a matter of fact, I had my panel replaced under warranty.
But the AC blower was still very weak and making bird chirping noise. I replaced both the blower and regulator. Problem fixed!
The BMW technician suspected things started going wrong with the regulator since he has fixed so many cars for that same problem.
FYI, the AC panel is $900.

Nicoromag 01-24-2013 06:01 PM

Great insight! I do get a noise too, but I would say it is more like a cycling wistling in my case. Mechanic said it could be a closed vent or stuffy AC filter, (wich I checked and were clean) no chirping for sure since noise is a on-and-off smooth but really annoying high-pitch vacuum-like noise.

Now, about that regulator, there is one on ebay posted at $100 with return policy, I'im thinking going down the list and eliminate possible scenarios, like you said, BMW tech guy believed it all started with that regulator so it may be worth give it a try.

I just turned the car on and the panel blinked like crazy and screen temperature was flashing back and forth from the set temp (74f) to 127f until I pressed the snowflake button (could be coincidence too) then it went back to uneven temperatures on each side of car. There's a used panel, from a front-crashed 750li that's compatible if needed.

You said it easy to replace the regulator, and I am decent on mechanic skills. Need to take the lower console apart perhaps? Hoping for that cheap fix I guess!

hd750Li 01-24-2013 07:41 PM

Be careful with used regulator unit. This part tends to go bad after a few years in hot+humid climate. If your AC blower has started making noise already, I highly recommend to replace it too. They are connected together by two screws.

See this video for a DIY:

sirstopher 01-25-2013 06:00 AM

If this is the part that sits ontop of the fan I think I have one.

I sold my car last week PM me

sirstopher 01-25-2013 06:02 AM

Chirping or rattle noise can be fixed by using a couple of drops of sewing machine oil at the bushing on top.

Nicoromag 01-25-2013 04:18 PM

Thank you for the info, I gave it a couple of test runs and didn't blink and after restarting the car after lowering temperature to 60f and fan to lowest driver's temperature accuracy improved greatly. Before going into a witch hunt swapping used parts (because I refuse to spend $850 in a new panel or regulator for the matter) I will wait and see how it behaves in the next couple of weeks. But i have a panel in ebay lined up just in case of frustration/panic attack.

Nicoromag 02-04-2013 02:00 PM

Ok, decided to go in a DIY used parts witch hunt after all. Replaced the regulator (ebay-new) and climate panel (ebay-low mileage), and no more "lights show" or blower shutting down by itself.

But temperature still uneven! Added freon and voila! A/C as good as new!!! (So far...!) YEY! Take that stealer! I mean dealer...

Thank you guys, without that video I could've never done it!

Ultimate745i 02-04-2013 03:30 PM


Originally Posted by hd750Li (Post 7336304)
If your AC blower has started making noise already, I highly recommend to replace it too.

No need for that...just shoot some WD-40 or 3-1 oil on top and bottom of motor shaft. Easy DIY fix! :thumbup:

Nicoromag 02-06-2013 12:05 PM

Btw, I did lube the shaft in blower, both ends with sewing machine oil and still hear a small rattle.

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