140 PWM fans wiring help

Ive recently fited some VW golf fans up to my 164 as they sized up quite nicely to the radiator and were significantly cheaper than SPAL option. unfortunately i am unsure how to get the PWM function to work. im hoping that maybe its the same prinicple as the modern volvo fans and someone could offer some insight.

i understand that the 4 wires are constant power, ground, 12V fuse (i assume coming from a temp sensor in the vw) and ECU PWM signal.

i bought a cheap pwm controller thats for pc fans thinking it would be the same principle and since the main power wires are not running through it, it should be fine. however i can only get them to operate on full speed which is great for summer but i dont imagine its great for the fans/controller.


  • Do you have a wiring diagram or specifications from the fans and controller?

    You may find the 4 wires on the fan are 12v power, earth, pwm signal, and fan rpm signal for pwm feedback.

    If the pwm controller is getting no feedback signal or the rpm from the signal is lower than expected by your controller then the pwm level would probably default to constant power in an attempt to increase rpm to expected level, explaining your symptoms.

    The PC fans your controller is designed for spin faster than car fans?

  • ab1Al @ab1 Melbourne

    Cooling fan wire diagram is for 2006 BPY engine, which is what you have. ElsaPro listed 2 wire diagrams, both look the same so I dunno why two are listed.

    This is how the wire diagram is labeled:

    Coolant Fan, Coolant Fan 2

    J... - Engine Control Relay

    J293 - Coolant Fan Control (FC) Control Module

    SA3 - Fuse 3 (on fuse panel A)

    SB38 - Fuse 38 (on fuse panel B)

    T2e - Double Connector, black, on coolant fan control (FC) (front end)

    T4d - 4-Pin Connector, black, on coolant fan control (FC) (front end)

    T40 - 40-Pin Connector, black, on electronics box engine compartment (Connector J)

    V7 - Coolant Fan

    V177 - Coolant Fan 2

    673 - Ground Connection 3 (on left front long member)

    B321 - Plus Connection 7 (30a) (in main wiring harness)

    * - ¿ Applicable Wiring Diagram for models with battery in engine compartment, engine codes AXX, BPY, BWA, BHZ, BZC

    ** - ¿ Applicable Wiring Diagram for models with battery in luggage compartment, engine codes BMJ, BUB


    SA3 is a large 50A fuse on the front side of fuse box in engine bay, third fuse from the left. Feeds the 6mm diameter red wire with white stripe (ro/ws) to fans/fan control module. As you can obviously see, it's the main power supply for the fans.

    SB38 is a 10A fuse that is probably power supply for the fan control module, feeds the 1mm blue wire with red stripe (bl/ro). Upper left corner in engine bay fuse box, 3rd from left. This fuse powers: Camshaft Adjustment Valve 1 -N205-, Coolant Fan Control (FC) Control Module -J293-. If you are getting power at pin 2 of the T4d connector at fans, then this fuse and the J... relay are probably okay.

    J... is labeled as engine control relay. Which engine control relay? Who the f*ck knows. I'm guessing that with the engine running, there's supposed to be a completed power circuit from it to J293. I can probably find it in the engine diagram, so if you have a problem with this circuit, let me know and I'll do some more digging.

    J293 is integrated with V7 which is the main cooling fan and controls the smaller fan V177.

    The black arrow just to the right of J293 is a continuation of the module onto the next page. All that is there is a wire to the module at the T4d/3 (pin #3 of 4-pin connector) connector, 0.5mm yellow with lilac stripe that is probably the control circuit from ECM connector T94/28. This circuit is likely communication so it probably won't have a regular voltage. If it operates like a LIN circuit, it will maybe be in the 10-11V range. If there was a communication error with the fan control module, there would likely be a dtc set in the ecm.

  • ab1Al @ab1 Melbourne
    edited October 2019

    this is grabbed from a vag forum... you may have a valid point re the pc fan speed with respect to the PWM controller. im not well equipped with knowledge of these circuit so i just assumed turning the knob on it adjusted the frequency of the signal to regulate fan speed.

  • That diagram key is probably okay if you're just trying to make it work in the original car, we probably need more detail to make it work in yours.

    Google revealed computer fans operate anywhere from 2000-22000rpm depending on application whereas car cooling fans apparently top out at 3500 rpm.

    You're likely of the right track with the adjustment thing. You may try adjusting the controller all the way in either direction to see if the fans will spin slower but most likely need a different standalone controller for automotive application with temperature input for PWM intensity.

  • ab1Al @ab1 Melbourne

    yes i will endeavour to find more detail unfortunately i didn't get a positive response from vw forums.

    here is the PWM controller

    as you can see it does not seem like its setup correctly for the application i am using so this may explain why it doesn't work as its expecting a signal wire

  • ab1Al @ab1 Melbourne

    it doesnt seem to have the tach signal output and pwm input unless these are the positive and negative motor labelled

  • That just looks like it has power to the controller, and power to the fan with all control through the dial. You may be able to hack some part of it to let you run the automotive fan.

    But I think you really need something with temperature dependent activation and power level.

  • Hi...after reviewing your case i can say If the yellow wire is a +12V PWM line, that makes no sense either. I can see the point of a PWM fan is to send 12V pulses of varying width to the fan thus controlling its current directly rather than traditional control with relies on adjusting voltage to control current. Your potentiometer is acting as a resistor between the +12V PWM and +12V constant lines.

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