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Thread: HEVAC: fans "hunting"

  1. #1
    Join Date
    Jan 2016
    Location
    Netherlands
    Posts
    152

    HEVAC: fans "hunting"

    Gents,

    For starters, it's winter down here, usually around 0c lately. Like most climate controls I know the range rover seems to not start blowing it's fans until the coolant temperature reaches at least the set temperature. Since a V8 is highly efficient the coolant get's up to temperature in no time and the fans kick in. When driving away from the house I need to make a few turns and slow down to the point that the car reaches idle again. I can understand the drop in voltage since the alternator can not keep up with power demands so the lights dim slightly and fans turn a bit slower, however, the fans go almost indiscernible. When I drive off again it takes a while for them to pick up again. Under certain circumstances the fans cut out when driving but usually only when the car has had a cold start. If I drive for a day (like yesterday, 850km) the problem never returns.

    So I am puzzled. The behaviour seems logical, perhaps the internal radiator cools to fast for the engine to provide more heat (seems unlikely) or the reduced flow cools the coolant in the radiator faster. Does anyone have / recognize this behavior or do I need to worry that my HEVAC unit is beginning to go?

    Cheers,

    -P

  2. #2
    Join Date
    Oct 2007
    Location
    Williamstown, Victoria
    Posts
    579
    I would be checking the battery voltage, battery terminals and alternator as a first point.
    P38's need a very strong battery to operate all the systems properly, from what you describe, it kind of sounds like not enough voltage present.
    Sometimes these things start happening and you barely notice them getting worse over time.
    Do your fans kick in when you switch the ignition to the second position without starting the engine?
    On mine, the the fans stop during engine start (as far as I can tell over the engine sound), then kick in again shortly after that, where they stay constant.
    If the battery and alternator check out ok, the next thing I would be checking the the fan relays, they may possibly be affected by the cold temps, then work normally once the engine bay heats up.
    That's what I would do first anyway!
    Hope that is of some help,
    Cheers, Pete.

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