A/C Amplifier Location

Discussion in 'Gen 2 Prius Technical Discussion' started by jerlands, Jun 7, 2019.

  1. jerlands

    jerlands Junior Member

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    I was able to test the ac fan and it runs correct. I didn't test the engine fan hower... probably would have been a good idea :) Anyway... does the AC system cause the engine cooling fan to operate or how does that work?
     
  2. ChapmanF

    ChapmanF Senior Member

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    Both fans should always run together. The relays switch the circuit around in a clever way, so both fans either run at low speed (they're electrically in series) or both at high speed (they're in parallel).

    Roughly, they run in low any time the A/C is on, or if the engine needs some cooling, and in high if the engine needs more cooling or the A/C line pressure goes over a threshold.
     
  3. jerlands

    jerlands Junior Member

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    Ok... both my fans do not run at the same time? seems this could be an amplifier problem and wonder if there is a way to do a factory reset on it? I've been under the car while it's running changing coolant and have noticed both fans on?
     
  4. ChapmanF

    ChapmanF Senior Member

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    If both fans don't run at the same time, that's a problem. It could be a wiring problem, a fuse problem, a fan motor problem, or a relay problem. One thing it can't be, if you look at the wiring diagram, is an A/C amplifier problem. The A/C amplifier doesn't have any way to make one fan run without the other one, even if it were messed up and wanted to.
     
  5. edthefox5

    edthefox5 Senior Member

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    Salved title infers the wiring is messed up to the fan if the car hook a hard front end hit and everything was crushed in.

    Fans run off relays.

    Or maybe the fan is dead. I would jump 12 volts into the fan if you are able to check it. Both fans must be on if ac on.

    The ac ecus I discussed earlier turn those fan relays on and off.
     
  6. jerlands

    jerlands Junior Member

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    I've run all the active techstream tests and on the "electric fan" I remember it now as simply on/off and not variable but it seems the test only was for one fan and only one speed?
     
    #26 jerlands, Jun 16, 2019 at 12:47 AM
    Last edited: Jun 16, 2019 at 1:08 AM
  7. jerlands

    jerlands Junior Member

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    The fan not running definitely now sounds like a problem so I'll have to check that out but I'm not certain about the "ac ecus" you're talking about?
     
  8. ChapmanF

    ChapmanF Senior Member

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    The A/C amplifier. (One ECU, two wire harness plugs that connect to it.)

    I remember for sure in Gen 1, both the A/C amplifier and the engine ECU got votes on switching the fan relays, and I think one or both of the engine coolant temp switch and the A/C pressure switch had direct representation too. But I haven't looked closely at a Gen 2 diagram to see what might be the same or different.
     
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