E38 auxiliary fan slow speed resistor repair

I am not an expert, so take all information and instructions on this page with a pinch of salt. It is quite possible that they will harm you, your wallet, your car, or all three. If in any doubt at all, take your car to the professionals. You have been warned.

The notes below refer to a 1998 EU model E38, but may be relevant to other BMW series/models of similar age. Note however, that also there are differences, e.g. later E38 models have a different fan controller using PWM (pulse width modulation), and these have no fan resistors at all.

If your auxiliary fan lost one or both of its slow speeds, but is OK on the highest speed, you have to replace one or both of the resistors on the auxiliary fan assembly. To access the fan remove the front bumper:


Remove the four screws (8mm skt.) from the wheel arch and remove the two large bolts (T50 torx) from the front of the bumper.

Press up plastic lugs and pull the bumper forward by 2~4 inches. Reach behind the bumper and disconnect fog lamps and  park distance control sensors. You may also have to disconnect the headlight cleaning system, if installed. Now you can pull the bumper further forward and remove it completely.


Detach connector from air duct by twisting it counter clockwise and then pulling it forward.

Unplug the connector and test the fan. The resistance between brown (1) and black/blue (4) should be ~0.3 Ohm; between brown (1) and black/red (3) ~0.5 Ohm; and between brown (1) and black (2) ~1 Ohm. If the two higher values are way off, in particular open circuit, then the resistors are probably faulty. You can also test the fan by connecting brown (1) to ground (-12V) and, one at a time, the other three to +12V.

If the resistors are bad, get 1x 0.2 Ohm 80 W Siemens Dale 353-003-01 and 1x 0.5 Ohm 85 W Siemens Dale 353-004-01, or get the BMW Aux. fan resistor repair kit P/N 67 32 8 371 873.

Once you established that the resistors are the culprits and got the spares, proceed as follows (I used the BMW kit - if you use separate resistors, you will have to cut and solder at different places, and will not have to take the plug apart):


Undo the seven screws holding the air duct. Take out the cable running across the front of the duct from the fixtures. Remove the duct. Release the four nuts holding the fan cowl and remove fan with cowl.

Remove four torx screws and take off grille.


Remove eight screws from brackets holding the resistors (N.B. two diffrent screw sizes).


Unless you happen to have the BMW special tool for taking pins out of the plug, go and feed the cat. From the side of the tin cut out a square bit and make a thin-walled tube with a diameter that matches the pins. Note down which wire goes to which pin. Insert the tube around the pin you want to remove and gently tap it out from the front side of plug housing. Also see Note 1 at the bottom of this page.

Remove the insulation and cut the wires as indicated. Pull out the old wires from the plastic tubes. Get the new resistor kit and feed the two new wires back through the plastic tubes. Arrange the resistors the same way as the old ones were positioned. Push the new pins back in the plug housing making sure they are not mixed up. It helps if you put a bit of Vaseline on the pin.

Put a piece of quality heat-shrink tubing on the thick wire coming from the plug and solder the three loose ends together. You will need a heavy duty soldering iron and you probably want to protect the other wires from the heat. Make sure the heat shrink tubing will not get heated too much while you do the soldering (as I almost managed to do). Once the joint cooled pull the heat shrink tubing back on it and heat gently until you get a good seal.

The finished resistor job.

Re-assemble everything in reverse order.

Some people found that without the fan working, the condensor could not properly cool the refrigerant so the high side pressure soared and the system dumped the charge. It is possible that you too will have to have the system recharged following the fan repair.

Note 1
An E39 owner used the above notes to repair his aux fan. He e-mailed me the following:
"One thing that caught me out was trying to push the pins out of the plug housing. It took me a while to figure out that there is a lock plate that you have to slide sideways with a small flat blade screwdriver to release the pins before you use the home made tin pin pusher."

If you find any mistakes or want to suggest additional info that I should include, please e-mail me.