Golf/Bora MK4 Fans Speed Controller

Prepared On:-

June 2007


Step 1
Step 2
Step 3
Step 4
Step 5


General Disclaimer

This information is provided as-is without any direct or implied warranty. Nime Consulting cannot be held liable for any loss or damage made to persons or possessions in connection with this information.

Customers that purchase a ready built fan speed controller are protected by a 90 day warranty against faulty parts and workmanship. Although every care has been taken to ensure that the product is both reliable and safe to use, Nime Consulting Limited cannot be held liable for any loss or damage made to persons or possessions in connection with the installation and/or use of the product.

The reader/purchaser must have reasonable judgement to the risks in the installation and use of this product. It is recommended that a competent auto electrician is tasked with or at least consulted for the installation process.




This installation guide provides an example installation of our Fan Speed Controller into a VW MK4 Golf. These instructions may be suitable for other cars based on the same platform (i.e. Seat, Scoda, Audi etc) it will be left to the discretion of the reader to determine whether this installation would be suitable.


The installer should be familiar with basic electrical wiring principles, and know how to make good connections and use insulating materials.



Step 1

Become familiar with the speed controller and it's three connecting wires. They are colour coded as Brown, Blue and Green, and have the following meanings:


Wire Meaning
Green/Yellow This is the ground connection. It should be connected to a good earthing point in the car.
Brown This is the supply connection. It should be connected to the low-speed input of the fans. In this example we have connected to this wire at the existing fan control module.
Blue This is the fan output connection. It should be connected to high speed input of the fans. In this example it is connected to the high speed fan connection on the existing fan control module.


Once the earth is connected, there are only two wires to worry about. The brown wire should go to the low-speed fan connection. The blue wire should go to the high speed connection.


The installer can choose where to make these connections. The low and high speed wires can be connected near the fans from under the car. Some people prefer this approach as it only touches wiring that is replacable with the fans.


The other approach is to wire directly to the loom that connects to the fan control module. This approach is easier, as it does not require access from underneath the car which usually means a quicker job. The only drawback with that, is you will have to connect to the exisiting wiring loom. This is the approach used here.



Locate the battery and remove the cover.


Figure 1. Battery exposed showing fuse box.




Step 2

Disconnect and remove the battery. Remove the battery fuse box. You can see the battery box in figure 2 below. It is made of a non metalic material and mounted to the car by the four bolts shown. Remove these bolts, and if present, remove the 10mm bolt securing the battery box to the air filter housing.

Figure 2. Battery removed

Step 3

With the battery box removed, it is possible to undo the two bolts holding the fan control module to the battery tray. The bolts are located in the bottom-left corner of the tray. They have already been removed in figure 3 below.


Figure 3. Battery tray visible

Step 4

With the fan control module bolts removed, carefully manouver it out from under the tray via the left hand side near the starter motor. Remember the direction of fitting of the controller.

Refering to figure 4 below, look at the fan control module and identify the supply and fan wires indicated in the picture. The nearest wire in the middle of the left hand connector is the low-speed fan supply. You need to connect the brown wire from the speed controller to this wire. You do not need to cut the wire. Simply remove some of the insulation from the supply wire and solder the brown wire to it, and cover the connection with insulation tape. If you can't solder, you can try using a press-on type connector like 'scotch locks' from Halfords. Failing that, you can simply bear enough copper wire from the brown wire to wrap in round the supply wire a couple of times and twist to secure.

Now, locate the high-speed fan wire on the right hand side. This is a heavy duty wire, as it needs to be up to the job of supply both fans with full power. Carefully remove some of the insulation from this wire, try not to damage too many copper strands.

Connect the blue wire from the speed controller to this wire. This wire is probably too thick for scotch locks, so they are not recommended here. Either solder, or bare enough copper from the blue wire so that you can wrap it once or twice around the thick wire and then twist together until secure. Insulate with tape.




Figure 4. Fan control module connections

Step 5

Connect the earth wire to one of the existing points. I have used the centre one.

The black device on the brown wire is an inline fuse, rated at 10A, and is there to protect the rest of the car's fuses and wiring should a fault occur in the speed controller.

There is a crimp on blue connector and a socket inline with the blue wire to the fan connection. These together allow quick disconnection of the device.

The whole box is stuck smooth face down to the battery tray using double sided sticky pads.

 The speed controller will fit comfortably on the battery tray underneath the battery box in the location shown in figure 6 below.

At this point it would be worth temporarily re-connecting the battery, ensuring that there are no loose wires near any moving engine parts, and starting the engine with the air-conditioning on. The fans should begin to turn at the low speed setting. If this is not the case, refer to the trouble-shooting section.

If all is well,  turn-off the engine. Remove the battery and then.

Figure 5. Completed Installation



With the engine running and the air-conditioning on (or climatronic) perform the following checks:-

  1. Connect a digital multimeter between earth and the brown supply wire. Is there at least 12 volts there? If there is proceed to step 2. If not, there is either a fault with the fan control module (relay) or the connection you made to it in step 4.
  2. Is the 10A in-line fuse ok? Check the resistance using the DMM, should be about 0 ohms. If blown, replace and try again.
  3. Is the earth connected propery? Yes? goto 4.
  4. Is the blue wire connected propery? You can perform a quick test of this by connecting the blue wire temporarily to the positive (red) terminal of the battery. Do this very briefly. The fans will try to run at full speed. If the fans do not run, you either have a problem with the wiring to the fans, or the fans motors are completely broken. If the fans do run, go to step 5.
  5. Connect a 12v 25w light bulb between the blue wire and a good earth. The light should come on and stay on. If the light does not come on, there is a fault with the speed controller, contact us to arrange a return.


Operating Voltage 12v-14.4v
Operating Current 6A at low fan speed
Operating frequency 9 Khz
Peak Current Capability 320 A
Power dissipation as heat Approx 3 W
Case temperature at 20 degrees C ambient temperature. Approx 30 degrees C.
Maximum operating temperature 100 degrees C.

(c) 2006-2020 Nime Consulting Limited.

Terms and conditions apply, click here for further details