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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 5 Series > E39 (1997 - 2003)

E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 01-04-2013, 09:02 PM
525e39 525e39 is offline
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Mein Auto: 2003 BMW 525i Sedan
Problems with 2003 e39 Aux Fan Install

I have a 2003 525i Sedan and had an Aux Fan that stop functioning. It would randomly start up and shudder before shutting down. I decided to attempt the fix myself thinking it was fairly straight forward.

I decided to purchase a TYC aftermarket fan.

Removal of the bumper and the existing fan was straight forward, but noticed that the connector on the new fan had all three wires inverted from what they should be. I pulled the pins out and reinserted them so they would line up correctly with the factory terminals on the female end. Figured this would solve the issue and I would be good.

As soon as I plugged in the connector the fan goes on at high speed. It doesn't shut off and the keys are not in the ignition. I let it run for a few minutes to see if it will turn off and nothing, it keeps running at the same high speed so I unplugged it and am stumped.

Would a bad temp sensor make it go on like this?

I read that the third smaller wire on the connector is the one which controls the speed on the fan, correct? Does this wire also make it turn off? I ask this because the 12v (Black Wire) seems to be always hot. What mechanism tells the fan to turn off?

Other Thought is maybe the controller on the TYC fan is bad? It is an external controller vs the built in controller the factory fan seems to have.

Any help would be greatly appreciated?
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  #2  
Old 01-04-2013, 09:46 PM
edjack edjack is online now
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Brown is always ground. The other wire colors should match up. The thin wire is the control line from the DME.
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  #3  
Old 01-04-2013, 09:56 PM
525e39 525e39 is offline
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That is what I read as well. It was shocked when I saw that the TYC unit had the wires pinned incorrectly.

I was also reading that there are Salmon colored relays by the fuse panel that may cause the unit to stay on all the time. I haven't been able to verify that this is the issue, but I may want to replace it to check.

So this DME wire should be what determines the speed of the fan and even if it is on or off which leads me to believe that the fan may not receiving the DME signal to turn off?

Last edited by 525e39; 01-04-2013 at 10:39 PM.
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  #4  
Old 01-05-2013, 03:02 AM
Mister Drexciya Mister Drexciya is offline
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Mein Auto: E39 2002 525iT
Correct: the DME defines if and how fast the auxiliary fan turns. The DME does not provide the power to the fan, only the control signal that goes -through a thin wire- to the power stage inside the fan assembly.

Simplified control circuitry:
http://www.bimmerfest.com/forums/att...hmentid=112488

As far as I know there is no relay that controls this fan or makes it turn continiously.

This is the most likely reason why your original fan was malfunctioning (just like mine did a few years ago with identical failure symptoms): burned electronics due to a combination of high-low temperature cycling and ingress of moisture:

http://www.m5board.com/vbulletin/att...an-auxfan1.jpg

There is a small chance that the DME control output circuitry will be damaged too when the fan's internal power stages fail, either by shorting the DME control output to ground or by reverse feeding 12V into the control output. Scanning error codes will tell you what exactly will be damaged.

Based on previous forum anecdotes I've read, on how your aftermarket fan behaves and that your aftermarket version has the pinout erroneously reversed, I'd say that this fan is not up to any quality at all. Return it and get the latest OEM version (Siemens or Bosch) from the BMW dealer.

It's better to go the OEM route than the aftermarket route concerning this fan. OEM lasts longer, is better mechanically balanced and it is less likely to damage the DME when it fails.

Last edited by Mister Drexciya; 01-05-2013 at 03:17 AM.
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  #5  
Old 01-05-2013, 07:58 AM
uncmozo uncmozo is offline
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I agree with Mr Drex - The fan is more complicated than you would think. Aftermarket, in this case, is only asking for problems. After I replaced mine, I opened up the old one. I was surprised to find the circuit board inside, I would imagine an aftermarket manufacturer would have a hard time duplicating that board.

Jerry
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  #6  
Old 01-05-2013, 10:02 AM
525e39 525e39 is offline
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So my first step should be returning the aftermarket fan and getting an OEM one. At that point am I good to just plug in the new fan and see if all works or is there a chance that I will damage the new fan by doing so?
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  #7  
Old 01-05-2013, 10:34 AM
Mister Drexciya Mister Drexciya is offline
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A failing fan may damage the DME control circuitry but the reverse will not happen; in that case your fan will never be turned on since there will be no control signal. So you are good to go by just putting in the new fan.
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  #8  
Old 01-05-2013, 04:05 PM
Mikes530 Mikes530 is offline
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Quote:
Originally Posted by 525e39 View Post
So my first step should be returning the aftermarket fan and getting an OEM one.
Yes. I replaced mine a couple of years ago with an OEM purchased online, simple plug and play.
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