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2010 2011 BMW 5 Series Forum F10 BMW 5-Series (F10) Forums General 5-Series Sedan and Wagon (F10 / F11) Forum Odd AC / Climate behaviour
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      04-23-2018, 03:36 AM   #1
Garethdphillips
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Odd AC / Climate behaviour

I'm experiencing some strange AC behavior and I am hoping somebody has experience of these symptoms, and may be able to offer some assistance.

Car is a 2010 F11. AC has worked perfectly for as long as Ive owned it (3 years ish) but developed an intermittant issue last week, when the hot weather arrived here in the UK. It was fine in the morning for my drive to the office, but then when I got into my car in the early evening, no AC. Over the past few days it appears to have followed a similar pattern. The AC works and cools as normal first thing in a morning, but then in the heat of the day when I most need it, it dies. Makes me think its temperature related? The car has been stood in the sun, though not running, and the AC doesnt work?

The symptoms are:

slight "mooing" noise from the AC. Can feel the car "vibrating" slightly. I think the engine fan is running really hard so could be what I can feel / hear. Even though the car isnt overheating as far as I can tell, and even though the car has just been started.

No cold air flow, but furthermore, the climate control seems to be going a bit mad, as even on full fan speed, the fans are barely blowing. Then they may suddenly spring to life and blow air really hard. Regardless, pressing the AC button just makes a faint "moo" noise. Very odd.

Nothing I can do seems to kick it into life, but the following morning or later in the evening, if I get into the car again, it will work perfectly.

Defintley seems to be related to the car having been sat in the sun, and the ambient temp rising ?
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      04-23-2018, 04:52 AM   #2
HighlandPete
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That does appear a strange one to identify.

Trying to think what could trigger the problem simply with sitting at higher temperatures... Wonder if a temperature sensor is faulting, once it is heat soaked from a hot day. Cooler... back to working OK.

Other area comes to mind with added heat soak, could be with the system somehow distorting/sticking, flaps won't function correctly, allowing progression of cooling strategy.

Hard to envisage how the A/C itself is at fault, as you say it is working at cooler ambient temperatures, unless it is sensor input related. Interesting to see what you find.
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      04-23-2018, 05:00 AM   #3
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Thinking of how to test the functions, assuming the high ambient temperature is stopping the A/C from cooling. Let's assume for a moment a feedback signal is indicating the A/C is overheated.

Have you tried for full airflows without the A/C function on? Simply to see if fans speed up, etc. Auto and Manual variations, changes in intensity, etc.

Does the MAX function do anything? Even if it is just high airflows, without real cooling, after running over 30 seconds or so.
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      04-23-2018, 05:19 AM   #4
Garethdphillips
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So when the ambient was high, and the AC wasn't working, I switched the function off, and was unable to get full fan speed. Going up to full did almost nothing, and it didn't give me any air flow. The fans weren't running either (its not as if there was a closed vent) . Suddenly they would start blowing hard again. It was intermittent. Makes me worried its electrical.

Its cooler today, I cant reproduce the issue, and the AC air is nice and cold.

I remember changing a "final stage resister" on an old E46 which made fan speed go haywire, kind of reminds me of that, but this seems specifically ambient temp related. And no idea why the engine cooling fan blows so hard when the AC conks (I can feel it in the car).

Very odd.

The main issue is that it isnt reproachable unless its hot outside. At least I think that is the pattern. Certainly feels like it.
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      04-23-2018, 05:45 AM   #5
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Quote:
Originally Posted by Garethdphillips View Post
Very odd.

The main issue is that it isnt reproachable unless its hot outside. At least I think that is the pattern. Certainly feels like it.
Agree it is very odd.

Does appear it may be getting an 'overheated' signal, the cooling fan working hard is a clue. Without knowing the full working strategy, difficult to know if the HVAC gets locked out until the temperature reading is back in range. Does appear the high ambient heat triggers a virtual shutdown, until the system cools enough to cycle correctly.
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      03-30-2019, 09:20 AM   #6
cals
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Quote:
Originally Posted by Garethdphillips View Post
So when the ambient was high, and the AC wasn't working, I switched the function off, and was unable to get full fan speed. Going up to full did almost nothing, and it didn't give me any air flow. The fans weren't running either (its not as if there was a closed vent) . Suddenly they would start blowing hard again. It was intermittent. Makes me worried its electrical.

Its cooler today, I cant reproduce the issue, and the AC air is nice and cold.

I remember changing a "final stage resister" on an old E46 which made fan speed go haywire, kind of reminds me of that, but this seems specifically ambient temp related. And no idea why the engine cooling fan blows so hard when the AC conks (I can feel it in the car).

Very odd.

The main issue is that it isnt reproachable unless its hot outside. At least I think that is the pattern. Certainly feels like it.
Hi - I’m having a similar issue ...... not temperature related, it goes on/off - did you ever find what was the issue in your car?
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      03-30-2019, 11:52 AM   #7
Barticus
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I had a similar issue with my 2014 530d last June. It started in the same way at the end of the day, and the a/c fan would work fine for 5-10 minutes and then steadily drop down to not blowing over a period of about 10 seconds. At first, it would resume after ten more minutes and then cut out again - repeat... After a few weeks it steadily got worse. It would usually work first thing in the morning, but rarely worked for more than 2-3mins when the day’s temperature had warmed up. It finally gave up and would not work at any time. BMW diagnosed a problem with both the fan controller resistor pack and the blower unit. Both parts were replaced and everything has worked properly since then.
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      03-30-2019, 07:58 PM   #8
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Thanks for the update.
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