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Thread: Cooling fans not coming on

  1. #1
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    Cooling fans not coming on

    So while in traffic yesterday, I notice the temp needle on gauge moving off center an creeping upwards - i punched up the a/c unit to HI and turned the blower fan on to high - this helped out. Seems the fans (on radiator) are not turning on, also turned the a/c down to LO, compressor turned on but fan action either. Is there a easy way to diagnose (bad relay, sensor, maybe the fans themselves - but to have both not come seems not likely.

    Thanks

  2. #2
    Registered User Aronis's Avatar
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    Turning on your A/C helped cool the car? Hows that work? I have had issues with old cars where overheating was helped by turning on the HEAT to full and opening all the windows, thus bringing hot engine water through the heat core for the heater and venting the heat through the open windows, but turning on the A/C would make more heat.....

    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

  3. #3
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    Turning on the A/C should force at least one of the fans on. If it doesn't, but the compressor comes on, then I'd be looking at fuses or a relay.

  4. #4
    Registered User Aronis's Avatar
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    cool.....
    Mike
    '18 BMW M5, '19 Porsche Boxster GTS
    (prior '94 325is, '97 M3, '00 A6 4.2,'03 RS6,'08 A4 Cab,'13 A8L,'15 Q7,'16 BMW M2,

  5. #5
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    I meant that I turned the heater on to HI and yes
    rolled down the windows. Will check fuses and relays
    next.

  6. #6
    Registered User mgmarsh39's Avatar
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    Sounds like the relay (switch) if both aren't coming on. If it went, there is potential damage to both fans. You can check by unplugging the fans, and running 12v to the plug and seeing if that kicks them on. If that works, the relay is bad. Otherwise, you're looking at about 2grand in fans . Ask me how I know.

  7. #7
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    Quote Originally Posted by mgmarsh39 View Post
    Sounds like the relay (switch) if both aren't coming on. If it went, there is potential damage to both fans. You can check by unplugging the fans, and running 12v to the plug and seeing if that kicks them on. If that works, the relay is bad. Otherwise, you're looking at about 2grand in fans . Ask me how I know.
    Ouch! Does anyone know if our fans interchange with other models at all, or are they RS6 specific?

  8. #8
    Registered User mgmarsh39's Avatar
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    They are RS6 Specific.

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    I'm going to check it out - can you un-plug the fan plugs from the controller unit with out having to take off bumper cover and move the front clip forward ? It could also be the controller unit ($400 ish).
    Thanks

  10. #10
    Registered User mgmarsh39's Avatar
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    Yes, its a bit of a headache but this is exactly what we did to determine my large fan and switch were bad.

  11. #11
    Registered User jtmdmd1's Avatar
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    Just replaced my small fan. Still not sure everything is working correctly since it doesn't seem to run for several seconds after the car is turned off like it always had. Maybe its just not hot enough this time of the year. They had tried direct wiring the fan & it didn't run- hopefully its not the controller too.
    2003 RS6 - Avus Silver Pearl - Ebony Interior - Warm Weather Package - Carbon Fiber - ACE TC - SE Exhaust

  12. #12
    Registered User lswing's Avatar
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    Quote Originally Posted by jtmdmd1 View Post
    Just replaced my small fan. Still not sure everything is working correctly since it doesn't seem to run for several seconds after the car is turned off like it always had. Maybe its just not hot enough this time of the year. They had tried direct wiring the fan & it didn't run- hopefully its not the controller too.
    My fans shut down right away when it's cold out or car isn't that hot. They really only run after shut down on really hot days or when driven hard.
    Ace/Edge TC - Tozo Trans - MTM TCU - REVO/ME7 tune - Wagner IC's w/ Venair Hoses - Aux Radiator delete - Hotchkis Sways - Hawk HPS Pads - Koni Sport Struts - Scroll KO4 Turbos - Devil's Own WM - 421whp/452wtq on Mustang Dyno - http://www.audirssix.com

  13. #13
    Registered User jtmdmd1's Avatar
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    Hopefully its OK- not getting the fan code, it just seems a little different sound wise when I shut down- it seems like its always hot down here in AL.

    Thanks
    2003 RS6 - Avus Silver Pearl - Ebony Interior - Warm Weather Package - Carbon Fiber - ACE TC - SE Exhaust

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