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Aux Fan or Pusher Fan is Dead

 
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loup



Joined: 15 Apr 2007
Posts: 1

PostPosted: Sun Apr 15, 2007 12:53 am    Post subject: Aux Fan or Pusher Fan is Dead Reply with quote

Help - I'm working on a 99 323 which has a dead electric cooling fan (the one in-front of the rad). I checked the voltage at the connector feeding the fan which showed 12V when the ac was on. So, I assumed the fan was dead. I replaced it tonight and it still won't come on. Relay? Has anyone seen this problem? I'm not sure which relay controls the fan motor. All 3 fuses check out in the glove box. Are there any wiring diagram available?
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edjack



Joined: 04 Feb 2002
Posts: 3887
Location: San Jose, CA

PostPosted: Sun Apr 15, 2007 3:24 pm    Post subject: Reply with quote

The fan runs when the A/C compressor runs. It also runs at a higher speed when the air temp through the rad triggers the sensor, usually located on the lower right side of the rad, on most models.

Some models have a resistor pack mounted on the fan to control speed; more recent models actually control the fan speed via the ECU. Not sure when the crossover began on the E46.

The control pins in the connector provide a ground to the fan. So, you should expect 12 V to be present.
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Ed BMW CCA member since 1987 (Nr. 62319).
'97 540i 6 speed Aspensilber over Aubergine interior.
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edjack



Joined: 04 Feb 2002
Posts: 3887
Location: San Jose, CA

PostPosted: Sun Apr 15, 2007 3:30 pm    Post subject: Reply with quote

Here's some more info, taken from Roadfly; it's for the E39, but there should be some pertinent info here:


Radiator Temp switch

OK guys, I guess at 140K miles, I'm going to be replacing several things over the next 4-6 months.

This weeks item, the aux fan isn't working with the A/C on. I tried jumpering the wires that connect to the temp sensor on the radiator. By jumpering the wires, I got the fan to run at med and high speed. According to the article in the "Tips & Tricks section, this should indicate the sensor switch is bad.

Am I correct?


That temp switch on the rad is only to activate the AUX fan if you are getting into an overtemp condition.

Otherwise the AUX fan comes on when the AC is on by an input from the AC controller and the engine computer combined - the actual operating design varies by model and year.

And the AUX fan will only operate if the outdoor temp is above 10C - as shown on the display in the instrument cluster.


If the AC clutch is active, and the temp is above 10C then I would suspect a fault in the AC system (pressure?) or in the electronics of the AC clutch driver circuit.

Cheers
Jim Cash


With the A/C running, the aux fan should be running at its lowest speed, the sensor/switch that you are considering replacing controls Med and High speeds, I would be suprised if swapping it out changes how the Aux Fan operates when the A/C is engaged.

My Aux Fan troubleshooting guide:
Your Aux Fan, if it works, has 3 modes, fast, really fast, and really really fast. Newer E39's may have a variable speed fan and these tips may not be exactly what you're looking for, I know that these tips are accurate for troubleshooting a 1998 540iA with a Nov 97 build date 

Fuses
For a 1998 540iA (check the guide in your glove compartment for your car), fuses 7, 20, 22, and 75 need to be checked. Fuse 75 (and 76 for the Heater Blower) are not easy to find, they are located behind the glove compartment and are accessed from underneath. Fully recline your passenger side seat and get on your back with your head in the footwell. As you look up behind the rear of the glovebox you will see 2 "Jolly Rancher" looking things, there they are. They are upside down from your view, meaning that they are inserted & removed from the top side that you can't see, removing them is easy, feeling your way back in is the tough part.

Does it run with the A/C on?
With your A/C on it should be spinning in the slowest of the 3 modes. You can confirm this by opening your hood with the engine running before you turn the A/C on, the electric fan in front of the radiator should not be spinning (assuming cold start-up). Go turn the A/C on, the fan should now start running.

Testing the fan motor & resistors
The Aux Fan will also engage if the coolant reaches above average temperatures:
91C - Low speed
104C - High Speed
We'll use this sensor input to test the fan and the resistors.

-Disconnect the 3 wire harness that goes to the Aux Fan temp sensor on the radiator right next to the coolant reservoir (the same sensor that reads the 91C and 104C temps).
-Start the car (or maybe you don't have to?)
-Connect the Brown wire to the Black wire that has the Red Stripe, your Aux Electric fan should now be spinning at medium speed. Note, if you connect the Brown wire to the Black wire with the White Stripe the Aux fan should spin as well, just at its highest speed. To test the high speed, get the fan going at medium speed, then while the blades are still spinning jump it up to high speed to avoid possibly blowing a fuse (thanks Jim Cash).
-Shut the car down and reconnect the harness to the sensor.

By jumpering at that point you are operating the relays that provide the power source to the fan. Relays are in the E box (under the passenger side microfilter). The resistors that control the lower speeds are located on the Aux Electric fan assembly.

If the Aux fan did not run at any speed, then I would first suspect that a fuse is blown, if you've checked the fuses then motor may have failed. If the Aux fan only worked on the highest speed, then I would suspect that one or both of the resistors or relays that control the lower speeds have failed (no resistors are used for the highest speed, but a relay is). It can be difficult to tell whether relay or resistor has failed, but resistors more commonly fail, so I would check that first. If you are experiencing overheating and the fan worked flawlessly, maybe the temp sensor (the one that you disconnected to jump wires at) has failed.

If your car is a older and still has the original Aux Electric fan I would be surprised if it didn't need replacement. I have a 98 and when I replaced it I found that the old motor was being choked with debris, and that 3 of the 6 armature magnets had come unglued from the motor casing and were working like little drum brakes to slow the fan down.

A new fan (complete assembly) can be had from Crevier BMW for about $240. You may be able to purchase just the fan motor from your local Autozone for under $100.

DIY replacement instructions: http://www.bmwtips.com/tipsntricks/auxfan/auxfan.htm
Additional Overheating help: http://bimmer.roadfly.org/bmw/forums/e39/forum.php?postid=3888947


Later,
Dave
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Ed BMW CCA member since 1987 (Nr. 62319).
'97 540i 6 speed Aspensilber over Aubergine interior.
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funnyceline



Joined: 11 May 2010
Posts: 1

PostPosted: Tue May 11, 2010 10:14 am    Post subject: Reply with quote

The fan could already be worn out. You can try to replace it and try to run the unit. If there a problem still, you really need to go to some experts to repair it.
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