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Discussion Starter #1
I have a 2001 e39 525i, my auxiliary fan does not seem to be working when the a/c is on and the clutch fan is very loud on acceleration. I have replaced the clutch fan with a new Merle clutch fan but that hasn’t changed the loud whoosh noise.
I unplugged the auxiliary fan and tested the power which showed 13.6v.
However when I turned the a/c off there was still 13.6 bolt at the fan connection. Is this normal and why is the fan not turning if there is current to it. The fan coupling is a three pin coupling. What is the black wire for? I am assuming to provide current is the engine overheats.
So basically, should there be 13.6v at the connector when the a/c is turned off and dies the fact that there is current to it indicate the fan is stuffed.
 

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Nuclear engineer
02/2012 X5 35d M57Y CPO 99K miles NOKIAN WR G3 12K miles
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The fan is a variable speed fan commanded by a Pulse Width Modulated - PWM - signal from the ECU over the skinny wire. PWM duty cycles 100% and 0% are reserved for troubleshooting signals. On start the ECU commands fan start and then listens for the signal generated by the turning fan coasting down.
 

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Discussion Starter #3
When you turn on the car the fan turns briefly then stops. It doesn’t turn on when the engine is at normal running temp.
If the fan has got 13.6 volts at the connector coupling, shouldn’t the fan be turning?


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Nuclear engineer
02/2012 X5 35d M57Y CPO 99K miles NOKIAN WR G3 12K miles
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No

There are three wires. The fat brown wire is the ground. The fat red wire is the power. The skinny wire is the command line to/from the ECU, much like the HVAC blower commanded to the FSU by the IHKA.
 

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Post #3 shows that the fan circuit is working correctly.

Your MY fan, as Doug has pointed out, is controlled by the DME, with an input from the rad outlet temp sensor.

Earlier E39s turned on the aux fan when A/C was commanded, and also when the rad temp sensor, in the right-side rad tank wanted more cooling.
 

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Under the lift arms
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the wooshing sound it good.. thats normal.. that tells you that your main cooling fan is on..

As long as you hear that sound when your pulling out your main fan is good..

The AUX fan is a PWM fan, and you cant not just apply power to the connector for it to work

The connector for the fan is live all the time, There are 3 wires, 1 ground, 1 dc positive voltage and one wire that comes directly from the computer, Advise : Dont go messing with it,

confirm you have power and earth, and then replace the fan, there is no fuses or relays
 

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The start-up fan test confirms that the fan circuit is working (post #3).
 

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Discussion Starter #8
I am getting very confused with this rolled up newspaper test. Some are saying the fan should stop at operating temp and others are saying it shouldn’t. Which is it.
And one other thing. If the aux fan is not working, will that cause the clutch fan to run higher?


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Under the lift arms
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If the aux fan is not working, will that cause the clutch fan to run higher?
YES

your main fan can handle 100% of the cooling requirements.. (assuming its in correct operational shape)

the aux fan is for the ac, the cat's and general engine bay air turn over,

Im not sure that the news paper test is..

BUT i can tell you specifically what to check to confirm that the fan is good or bad

I can also show you what fan i bought
 

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Discussion Starter #10
I have just put in a new Merle 3 pin clutch fan because the old one had a bearing rattle and also it was quite loud.
The fan is a correct oem part. But I have read two different posts about whether you should be able to stop the fan using the newspaper test. It is simply pushing some rolled up news paper into the fan when it is running at normal temperature. If the fan stops it either indicated the fan is good or bad. The question is which is it. Too many different posts to draw a conclusion. Mine doesn’t stop but I don’t know if that is because the aux fan isn’t working


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Wingnut
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newspaper test if for the mechanical fan clutch fan, not for the electric aux fan. im a little confused on what youre doing, whats a 3 pin clutch fan?
 

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Discussion Starter #13
3 pin is the connector point, some are four pin.
Pre 9/98:
4 pins; Ground and 3 voltage lines thru pre-resistors (and relays).

Post 9/98: 3 pins; Voltage, ground, PWM signal from engine ECU (DME/DDE).


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Wingnut
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ok, but thats the aux fan wiring. you stated fan clutch. just trying to figure out which fan youre doing the newspaper test on. newspaper test works on the clutched fan only, on a warmed up engine it should stop the rotation of the blade with the engine running.
 

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Discussion Starter #15
Ok, I can see how u have confused everyone. I was trying to work out if there was a link between the non working aux fan and the clutch fan not disengaging.
Apparently there is no link. I just had a stuffed aux fan and a binding up clutch fan,

So my fix was to replace both. Sorry for the confusion


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Hi, I just wanted to add that I've had similar problems with the AUX fan in my 2001 530i.

My aux fan would work only intermittently during the summer months (which I know you're in now) but generally would not engage, including when the A/C was running at slow driving speeds during high heat days. My AUX fan would also not ever respond to the pulse check at startup and I had an aux fan error logged in PA Soft. Visual inspection of the wires revealed nothing obviously wrong. This told me that my power, ground, and DME wires were good, but that something else was causing my AUX fan to not work most of the time. I thought it was really odd that my fan would not perform the pulse check but would still manage to turn on at apparently random intervals.

The general consensus from the community here was that my AUX fan was probably bad. I intend to replace it once we get closer to summer here.
 

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Hi, I just wanted to add that I've had similar problems with the AUX fan in my 2001 530i.

I thought it was really odd that my fan would not perform the pulse check but would still manage to turn on at apparently random intervals.

The general consensus from the community here was that my AUX fan was probably bad. I intend to replace it once we get closer to summer here.
I had an '02 touring in which the "random intervals" when the AUX fan turned on were overnight and it would randomly kill the battery. Also hard to diagnose because often the "on" was a very slow fan speed and quiet.
 

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Discussion Starter #20
I have no idea how your aux fan can be coming on overnight unless you have a wiring short somewhere,


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