AC cool only when moving

Discussion in 'Gen 2 Prius Main Forum' started by picassopigeon, Jul 11, 2020.

  1. picassopigeon

    picassopigeon Junior Member

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    My AC is only cooling when we're moving. If we are stopped in traffic or parked for a while it starts blowing warm air.

    There are no radiator fans running when I first start the AC, then when the engine warms the radiator fan comes on and we get cool air at a stop.

    It feels as though both radiator fans come on at this point. As I can feel them sucking air through the front.

    Thanks for any help.

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  2. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    That's a problem.

    There are 2 fans up there, one is primarily for A/C performance. It should always run when the compressor is on.

    The other fan is for your engine and inverter, and it also pulls air through the front. I'm betting that only that main fan is working in your car, and the A/C fan has quit.
     
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  3. picassopigeon

    picassopigeon Junior Member

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    Thanks for your reply. Is this an easy fix?
    Is there a test procedure for checking the fan?

    Thanks again for your help

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  4. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    for a UK-spec car I'm not sure what your options are for official repair manuals- the factory in Japan wires your models a bit differently than ours and I don't want to mislead you with invalid info.

    Fortunately in a general sense this isn't a complex system; Toyota uses the same conventions as nearly all other automakers. Usually you just need to check for voltage at the fan power connector to see if 12v is making it to the fan. If yes, then the fan has gone bad and it's not a terrible amount of work to replace.

    If there is no power to the fan connector, more detective work will be required to determine if this is a relay, fuse, wire, controller or combination failure.

    But if you can locate the fan power connector and put a simple voltmeter on it yourself, you'd be ahead of the game.
     
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  5. JSchnee

    JSchnee Junior Member

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    My AC is definitely less cold when stopped versus when moving. 2012 Gen3 Model 3. I’ll have to check and see which fans are running,


    iPhone ? Pro
     
  6. ChapmanF

    ChapmanF Senior Member

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    The wiring of the Gen 2 fans was described in some detail in this post.

    Like the generations before and after it, Gen 2 used a series/parallel arrangement where both fans always run together. They either form a series circuit, making them both run at low speed, or if more cooling is needed, an SPDT relay switches and makes the circuit parallel, and they both run at high speed.

    If you ever see just one of them running, there is a connector, wiring, relay, or fan problem. (I didn't say fuse problem, because even if a fuse is blown, that only means that somewhere else, there is a problem.)

    Sometimes you can narrow down where the problem must be by careful observation of which fan runs and when. If the problem is in the series circuit, what can happen is neither fan runs, until the car decides it's hot enough to need high-speed, and then the one fan that runs will start.

    The diagrams have often labeled one of the responsible ECU terminals "RF" (radiator fan?) and one of them "CF" (condenser fan?), but those labels are a bit weird given the way it's wired as described above, and that the two fans are side by side, very similar, and both of them pull air through both the condenser and radiator.

    For least confusion, it's easiest to describe which fan is running by the color of its wires. That way those following along at home in the wiring diagram don't have to remember "hmm, last time I saw a Gen 2, which side was the green-stripe one on?"

    I can't argue with Leadfoot about the possibility of UK wiring being different ... I've never heard that it is (where these fans are concerned), but I also don't know that it isn't.
     
  7. picassopigeon

    picassopigeon Junior Member

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    I've had techstream connected to the car today, this has options to switch on the fans individually.
    Both fans will work through techstream.

    The AC compressor will run from techstream, and will match the speed the speed that you call for.

    After checking these things I switched on the AC system with the windows open and at max cold, I could hear the fans cycling on/off and the temperature of the evaporator went down to 7⁰C this gave nice cold air in the cabin. After a while the fan cycling stopped and the evaporator temperature increased, the fans would not cycle up to full speed again.

    Any ideas why it would be an intermittent problem?

    Thanks

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  8. bisco

    bisco cookie crumbler

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    maybe a bad fan temp sensor?
     
  9. picassopigeon

    picassopigeon Junior Member

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  10. picassopigeon

    picassopigeon Junior Member

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    Or it did. Now after a restart this is no longer the case. Fans running only at low speed

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  11. ChapmanF

    ChapmanF Senior Member

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    If the fan with the green and white wiring is able to run at all ever with that relay removed, then the UK wiring must indeed be completely different from the way it's wired here.
     
  12. bisco

    bisco cookie crumbler

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  13. picassopigeon

    picassopigeon Junior Member

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    Yes right hand drive UK vehicle.
    I'll check again tomorrow, about the fan with the green wires, if the rain holds off.


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  14. ski.dive

    ski.dive Active Member

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    Have you checked if it is Low on Freon?
     
  15. picassopigeon

    picassopigeon Junior Member

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