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HV battery inactive cooling fan fix

Discussion in 'Gen 2 Prius Main Forum' started by lexidium, Nov 27, 2021.

  1. lexidium

    lexidium Active Member

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    2008 Prius.
    Cooling fan was not working. Tested fuse and relay and fan and they were all good.
    Tested the wiring as far as I could but couldn't find anything so I had a word with the hybrid mechanic and he told me it was a very common fault that the plug and wiring behind the panel on the passenger side was a source of damp and corrosion.
    I hadn't suspected at all that there was a connection on that side of the car and thought all the faults would be on the side where the motor was. None of the Youtube vids showed this.
    Sure enough, the wires at the plug were corroded so I fitted spades and bypassed it. All works fine now and I have taken SFO's advice and customised TORQUE to run at 6 speed so whenever I'm on the motorway for a while, I can switch it on myself. Thanks SFO.
    I've now found another thread from about 5 years ago saying the same thing with pics:

    HV battery cooling fan fault and fix | PriusChat

    The reason I am putting all this down is that I spent weeks arsing about with it through ignorance and
    I hope it may help others.
     
    SFO and bisco like this.
  2. mr_guy_mann

    mr_guy_mann Senior Member

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    Nice. Did you seal the tiny cracks in the body at the top corners of the tailgate opening that caused the corrosion in the first place?

    Posted via the PriusChat mobile app.
     
  3. edthefox5

    edthefox5 Senior Member

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    Pretty common. You have a leak in the hatch corner like all g2s.
    Rains…..water leaks into the cabin and tends to drip on that connector corroding it.
    Now for more fun check out the goldfish pond your 12 volt battery is sitting in cause that’s where all that dripping pools. Take the 12 out drain the hole by pulling out its drain plug. Water under the spare tire too.

    Hundreds of posts about found inthe search forum link up top.

    Search

    hatch leak
     
  4. Tombukt2

    Tombukt2 Senior Member

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    Yes I have all those drain plugs out and laying in their respected holes just in case somebody might want to put them back in but I haven't had the corner of the hatch leak yet I do keep it brushed off and blow it off with the hose often make sure there's no leaves and garbage up in there broken twigs stuff that can't get past the strut mounts and what have you keep it whistle clean if possible don't park under trees easier said than done

    SM-A715F ?
     
  5. Seaside Harry

    Seaside Harry Junior Member

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    When I rebuilt my 2005's traction battery last year, I had the same problem with the same Molex connector. On my U.S. model, this connector is positioned adjacent to the battery fan and actually attached to the fan bracket. I've seen a number of photos showing what appears to be this same connector--with the same two corroded terminals--on the opposite (passenger) side in UK versions of the Gen 2 Prius.

    My car has the usual leak, which allowed water to collect in the bottom of the 12V battery well until I opened up the drain hole, but I don't think moisture is the problem with this connector. Neither my connector nor any of the surrounding surfaces show any discoloration, rust, corrosion, or other signs of water incursion--just those two ugly terminals for the coil side of the fan relay. I suspect that Toyota simply undersized these wires & connector contacts for the repeated current surge they endure every time the relay is energized, eventually burning out the wires/pins inside the Molex connector. When this happens, the relay no longer operates, the fan never comes on, and the battery overheats. In my case, this resulted in the red triangle of death (P0A80) and a completely failed, non-chargeable module.

    Along with replacing that module and a couple of weak ones, I bypassed the relay connection with a heavier-gauge version and the car is still running strong after 16 months and 5000+ miles. Hope this helps.

    IMG_6898.jpg IMG_6900.jpg IMG_6927.jpg IMG_6929.jpg
     
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    I'm not sure one way or the other, but I'd be inclined to not override the car's computers, think I know better when the fan should be running, and how fast.
     
  7. lexidium

    lexidium Active Member

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    There is an idea - and I agree with it - that if the batteries are kept cool, they will have a longer life. Leaving them to get to 96 degrees or so before the fan kicks in at No 1 I'm not sure is the optimum thing for old batteries and I've observed that it doesn't really cool them down much at that speed but just stops them getting much hotter.
    If it were to shorten the life of the fan - and it's already 14 years old - it's easy and cheap to change.

    I don't leave it on all the time but fifteen minutes on my motorway journey keeps it nice and cool.
     
    Mendel Leisk likes this.