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Thread: Radiator fan runs continuously

  1. #1
    Join Date
    Mar 2011
    Posts
    14

    Default Radiator fan runs continuously

    Hi,

    I have a problem with the radiator fan running continuously.

    History: Problem occurred a few months back and the mechanic replaced the high pressure A/C sensor. This stopped the radiator fan running all the time and also fixed the lack of cold air from the air-conditioning.

    However, the problem has come back with the radiator fan.

    Anyone had this problem and do you know the fix?

    Thanks
    Andrew

  2. #2
    Join Date
    Apr 2011
    Location
    michigan
    Posts
    5

    Default

    I have opposite problem--my fan never turns on, even when engine is hot as hell. If you can find the engine temp sensor (I dont know where it is), try unplugging it, then try unplugging the fan relay. the relay might be stuck closed.

  3. #3
    Join Date
    Mar 2011
    Posts
    14

    Default

    A lot of people of this forum and Matthews have had the same problem. They describe the problem but no answers come up and then they do not return to point out the answer. Please, does anyone know?

  4. #4
    Join Date
    Sep 2002
    Location
    Belgium
    Posts
    2,362

    Default

    I believe the most common cause of a radiator fan either not running or running all the time is a failing
    driver module. This is a (darlington) transistor circuit and can fail open or short.
    However, since Andrew's problem was (temporary) fixed by replacing another part, this seems to indicate
    the problem may very well be something different.
    The module (item 4/71 in the pdf) is part of the fan assembly itself and can't be replaced seperately :-(
    Willy
    144 GL (1974)--->244 GL (1982)--->940 GLE 2.3i (1992)--->XC70 2.5T (2004)--->XC90 T5 (2018)

  5. #5
    Join Date
    Mar 2011
    Posts
    14

    Default

    Thanks for the replies. According to Volvo mechanic, when the pressure in the aircon gas goes below a certain PSI the radiator fan switches on by direction of the high pressure sensor. As to why an idiot would design a system in this way is beyond me.

    Found a leak in the condensor. Evidently fixed although something tells me I'll be back.

    For the record, mine is a 2005 XC70 with 75.000kms on the clock. I have never had more problems with a car. Volvo truly are crap.

  6. #6
    Join Date
    Feb 2010
    Location
    Virginia Beach
    Posts
    3,757

    Default

    Sorry you're having trouble with the car, the Volvos that I have owned have been more reliable and cheaper to own than my friend's BMWs (Bring My Wallet) or other european cars.

    But to your question on why the AC can switch on the fan - it's pretty simple. Look where the condenser is located: just in front of the radiator. The AC efficiency depends on the condenser being able to reject heat and condense the freon, so that it can be evaporated inside the car to remove the heat from the air blowing into the passenger compartment. If there is not enough air moving across the condenser, then the cycle doesn't work because the freon isn't cooled enough.

    In that case, the radiator fan kicks on to draw air across the condenser. One fan, two uses - efficient engineering....
    Current Fleet:
    2016 Tundra Crewmax 4WD 1794
    2005 MB S600 (100K, Michelin AS3+, M1 0W40)
    2002 V70-XC (238K, Castrol Edge 0W40)
    2002 V70-T5 (195K, IPD bars, Bilsteins)
    2001 V70-T5 (76K)
    1932 Packard Sedan (straight 8, dual sidemounts, original paint and interior, Shell Rotella 15W40)

  7. #7
    Join Date
    Mar 2011
    Posts
    14

    Default

    Thanks Astro. But if there is no gas in the AC and they took the effort to place a high pressure sensor on the system, why not just shut down the AC through the computer and send an error message. Making the radiator fan go to max is just stupid and inefficient.

  8. #8
    Join Date
    Sep 2002
    Location
    Belgium
    Posts
    2,362

    Default

    Quote Originally Posted by millsa99 View Post
    Thanks Astro. But if there is no gas in the AC and they took the effort to place a high pressure sensor on the system, why not just shut down the AC through the computer and send an error message. Making the radiator fan go to max is just stupid and inefficient.
    Perhaps, but this is still in the assumption that it is indeed the A/C system that keeps
    the fan running and if I am not mistaken, this is not (as yet) proven.....
    Therefore, it may useful to keep an open mind as to the cause of the problem.
    Willy
    144 GL (1974)--->244 GL (1982)--->940 GLE 2.3i (1992)--->XC70 2.5T (2004)--->XC90 T5 (2018)

  9. #9
    Join Date
    Sep 2010
    Location
    Tucson, AZ
    Posts
    13

    Default

    I am late to the party, but I find that, on occasion, my radiator fan and/or my blower fan (for cabin circulation) will operate of their own occord. My independent Volvo mechanic tells me that there are temperature sensors for both situations that will cause the fans to operate to help keep temperatures under control. And a friend who is a technical writer for BMW tells me the same thing about that brand.

    And in both cases, this information is not contained in the operators manuals, so owners think something is wrong, thereby spending precious funds at the dealership for no good reason.
    2002 Volvo V70XC
    - Blue
    - 90k + miles

    2012 Ford F150 Crew Cab 2WD
    - Company Truck White
    - 6k + miles

    1969 Mercedes 280SE - DONATED...such a mistake.
    - Havana Brown
    - 130,000 miles
    - family owned since new & garage bound for the last ten years.

  10. #10
    Join Date
    Dec 2009
    Location
    NJ
    Posts
    39

    Default

    I had this issue about a year ago. Fan ran nonstop, even after parked in the garage for 2 hours. I disconnected battery to keep it from running down and went to a good local indy. They told me, as Willy said above, that the controller couldn't be replaced independently of the fan. They replaced complete fan assembly and all has been fine since.... at least with that portion of the car. Kind of a drag that the controller can't be replaced w/o trashing what is otherwise probably a fine fan assembly.

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