AC fan cuts off

[one 35i]

AC fan cuts off sporadically. Only stays off for a second or so and then come back on and might go several minutes before it repeats. Any ideas or anyone else with the same problem??:iono:

[trashcan]

Silly question but do you have it on auto?

[one 35i]

I see where you are going--I think. So if on auto it is cutting on and off to maintain the selected temp. I feel dumb for not realizing the relationship. Guess I am still in awe with the car! Thanks for the hint.

[jeremyc74]

Originally Posted by one 35i

I see where you are going--I think. So if on auto it is cutting on and off to maintain the selected temp. I feel dumb for not realizing the relationship. Guess I am still in awe with the car! Thanks for the hint.

My fan doesn't cut off, even in auto. If it's stopping completely, I'd take it in, because something isn't right.

That said, if you're at a stop light with it on full speed, it will drop a little when you first pull out. I'm guessing the alternator voltage drops a little at very low RPMs. The fan speed changes, but it picks right back up, and never turns off.

[plien69]

I have also noticed that my fan blower intermittently cuts out for a second or so, every once in a while. I rarely run with the A/C compressor on, so I don't think it's related to that.

I think it's related to efficiency-related designs such as Intelligent Alternator Control and an electric water pump:
http://www.edmunds.com/insideline/do...leId=115127#16

Perhaps the car needs to briefly reduce power to the HVAC blower motors as it manages the electrical system of the car in conjunction with the alternator and the electric water pump, among other systems.

[drewser]

I noticed mine doing that several times in Europe, set at around 62 on both sides. Outside temp was probably 80 or so. I can't remember if it was set on Auto or not.

I'll test it again when the car comes in (hopefully next couple of weeks). Glad to hear I'm not the only one who has experienced it though.

[1ToBeOn2Wheels]

Yes, I thought I was imagining this! Mine does this too, mostly when the AC compressor is off. I wondered if it was related to the power steering, as I've noticed it while making turns.

[tonytigerking]

On my car, the fan cuts off for a second and on again too, when the a/c is off. It doesn't do that when the a/c is on.

[Esmallstii]

Same thing happens to mine too. It is in for Service right now, and I told the Service mgr about it. I'll let you know what they come up with.

[BimmerSkunk]

Anyone ever get a solid answer on this? Mine does it too and the fan speed seems to surge at times. It's not as severe as when the final stage resistor went on my e46 though.

[AW128i]

Which fan is the OP talking about, the radiator fan or the HVAC fan? The radiator fan does not run at a constant speed, even with the A/C on. The HVAC fan doesn't ever cut out on my car unless I turn the system off completely. The HVAC fan does slow down when the car speed slows and then will speed back up once the car is underway again. That isn't really noticeable unless the fan is at one of the higher speeds. From what I recall reading in technical documents about the system, the HVAC is designed to operate this way to help cut down on noise levels when the system is on. The automatic climate control systems in modern VWs and Audis also do this.