Cooling Fan Module?

Discussion in 'Mk5 VW Jetta, Sportwagen, and Audi A3 TDI forum' started by 14racing, Jul 7, 2012.

  1. 14racing

    14racing New Member

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    Just wondering if the cooling fan module was built in the large fan motor? My fans stay running all of the time even with the engine off. Will not quit unless I pull out the fuse. I do have a fault for the fan control module and by the looks of the schematic I have it looks like it s built in the fan. Is that correct? I'm thinking I need a new large fan. Any thoughts on this?
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  2. 14racing

    14racing New Member

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    Nobody on here knows?
  3. Keithuk

    Keithuk Super Moderator

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    It won't be built into the fan. If the cooling fan runs all the time then it sound like the switch is stuck on it, just unplug it.

    If you google it you will see pics.

    Car: 2006

    Please add the model to your car spec then I can investigate more?
  4. 14racing

    14racing New Member

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    It's a 2006 jetta tdi
  5. Keithuk

    Keithuk Super Moderator

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    Please add Jetta to your car spec?

    Do you happen to know the engine code its normally of a sticker on the timing belt cover or on the Options sticker?

    Jetta (05>) 1.9D TDI PD (2005-07), Engine code: BRM

    The wiring diagram only lists.

    Engine bay 2, Engine fuse/relaybox

    F3 (50A) Engine coolant blower motor
  6. 14racing

    14racing New Member

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    its a brm. When i got the car the 50amp fuse was blown. I put one in it and the large fan runs continuously. The small fan for the condensor turns off and on like it should. The large fan will not stop until I pull out the 50 amp fuse. So os is a separate temp switch to turn the fan on other than the coolant temp switch which gives me the reading on the dash?
  7. Keithuk

    Keithuk Super Moderator

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    That was a good guess BRM.

    Don't you have a temp gauge in the dash just a warning light?

    If you disconnect the fan switch on the radiator and the fan stops then that switch is faulty.

    The only wiring diagram I can show you is from a mk2 Golf/Jetta. somethings might be the same.
  8. 14racing

    14racing New Member

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    I have a temp gauge. I'll check the switch. thanks for the help.
  9. Ol'Rattler

    Ol'Rattler Active Member

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    There is no switch for the fan. The fan is controlled by a digital controller. If the fan won't shut off, then either the controller is faulty or the controller is receiving a signal from the ECU commanding the fan on all the time. VCDS would help in diagnosing the problem.

    IIRC, the controller is part of the big fan. Of course if the big fan is blowing fuses, then it probably is shot and needs to be replaced anyway.
  10. Ol'Rattler

    Ol'Rattler Active Member

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    Checked my paper Bentley's and as near as I can tell, there is a temp sensor on the radiator that inputs to the ECM and the ECM commands the fan controller on and off. Unplugging the sensor might tell you if the sensor is causing a problem or it might not.

    I would be leery about grounding the wire to troubleshoot, though, the other end of the wire goes to the ECM and grounding it might fry the ECM.

    There is a reference in the diagrams about a"thermal switch" but I couldn't find it in the diagrams. I think the thermal switch may only be on the gassers but IDK.

    When I get a chance I will look in the diagrams on my CD version of Bentley's. It's laid out a lot better than the lame paper version.

    What is the manufacturing date of your Jetta and do you know if you have 1 speed or 2 speed fans?. If you have air, you probably have 2 speed fans, but once again, IDK.
    Last edited by a moderator: Jul 10, 2012
  11. Ol'Rattler

    Ol'Rattler Active Member

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    CD Bentleys shows the temp sensor as a switch and the 2 wires on it go to the ECU. One yellow one Brown. Probably the safest for the ECU would be to unplug the connector and check continuity between the 2 pins on the sensor. The diagram shows the "off position" of the sensor as contacts open so I would assume that continuity through the sensor with the car cold would indicate a bad sensor.

    The temp sensor for the fans is located on the lower cooling hose near the radiator, not on the radiator like the text in Bentley's says.

    There are two red wires on the controller, the big red wire goes directly to fuse SA 3 (50 amp) and is always hot. The the small red wire goes to fuse SB 24 (10 amp) and then to the B+ Terminal 30 power supply relay. The green wire on the fan controller goes to the ECU and the big brown wires on the controller goes to ground.
    Last edited by a moderator: Jul 10, 2012
  12. 14racing

    14racing New Member

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    I tried unplugging the temp sensor and the fans continue to run. The controller must be stuck. I assume I need to replace the large fan then? I did run a scan on all of the modules with my vag-com and I did not have any faults. I'm still kind of learning how to use it though. It's much different then what I am used to.
  13. Ol'Rattler

    Ol'Rattler Active Member

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    So take it one step farther and T/S the sensor to better understand the system and to rule out the sensor. It could be that sensor contacts open = fan on and sensor contacts closed = fan off. IDK.

    If you check for continuity between the 2 pins in the sensor when the car is cold and you get no continuity, then that could support the fact that with the contacts in the sensor are open then the fan should be turned off. You could buy a new sensor (relatively cheap) and run continuity on it to verify that the sensor contact are open when the sensor is cold.

    It might not hurt to post in the VCDS forum for specific advise on how to check the cooling fan system. My suspicion is that your controller is bad, but I am not sure how to prove it so that you can verify the controller is actually the problem.
    Last edited by a moderator: Jul 12, 2012
  14. pantonio93

    pantonio93 New Member

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    I have been having the same issue the 50 amp fuse was blown now that I replaced it the fan is always on I was wondering what you did to fix it?
  15. tdi-09

    tdi-09 New Member

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    did you ever fix this issue?
    im on the same boat, fan wont shut down.
  16. Ol'Rattler

    Ol'Rattler Active Member

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    If you can figure out which controller controls the fans there might be a measuring block that reports the sensor temp and perhaps a measuring block that reports if the fan is commanded on.
  17. mark6556

    mark6556 Member

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    I have been exploring a different radiator fan problem, but some of what I've found may be helpful here. VCDS appears to read two different coolant sensors: The G62(engine) under the engine module tab in VCDS and another unlabeled one under the HVAC module tab.... I assume this is the radiator coolant temp sensor(G82) as it reads a slightly different value than the G62(and this was with the car sitting in the garage for days without the engine running). Looking in the manual, it claims this sensor is on the drivers side bottom of the radiator... I could not see it and it does not appear to be in the spot as shown in the manual but could have been buried in the front or underside of the radiator where I cannot see well.
    I ran some experiments to try to understand better how the large fan is controlled by the car. The heavy red and brown wires carry battery power to the fan and provide power whether the ignition is ON or OFF. The small diameter black wire(on the fan side of the connector interface) also carries positive battery power to the fan but is switched on and off with the ignition. I believe this powers the fan's internal control circuit but does not provide bulk power for driving the fan(that is provided by the heavy wires). In all my tests this wire followed the ignition state regardless of anything I did. When I run the VCDS fan output test with the fans plugged in, the green wire appears to carry an 8 volt or so PWM(pulse witdth modulation) signal from the engine controller to the fan. I put an oscilloscope on this signal and watched it ramp up from around 10% to 90% duty cycle during the VCDS fan test (under output tests). When the fan is unplugged and I run the fan test, the duty cycle does not increase.... so the car can detect if the fan is not connected and the ECU will not drive it in that scenario.

    I think in your particular case, I'd check the output of the green wire referenced to battery ground/heavy brown wire(with the connector unplugged looking at the vehicle side connector)... you could measure it with a volt meter... I was reading maybe 300mV for the 10% duty cycle.... if your ECU output is stuck on or shorted to +12v, it would be a lot higher voltage than 300mV. If that checks out okay, then use VCDS to check your coolant temp under the HVAC tab(assuming this is G82) and see if it reads room temperature after your car has sat a while. If that looks fine, I'd replace your large fan. Autohausaz.com has the best price I could find.... I just ordered one from there myself a few days ago.
  18. Keithuk

    Keithuk Super Moderator

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    Coolant Temperature Sensor (G62)
    Coolant Temperature Sensor at Engine Outlet (G82)

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