Engine revs high when AC is on. Is this normal?

Discussion in 'Gen 3 Prius Technical Discussion' started by Kusumar, Sep 19, 2021.

  1. Kusumar

    Kusumar New Member

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    Lately my engine revs high when I blast the AC. I live in California so slightly rolling down the window with the AC on low is usually okay. I’m an Uber driver(shocking lol) and passengers are always ask to blast the AC during the daytime ever since summer came when temperatures rose. But I noticed that my engine idles high since in the last few months. It’s actually preventing me from driving during the day because idk if it’s a problem with the engine or not. When I crank the AC at night, the same thing happens.
     
  2. ChapmanF

    ChapmanF Senior Member

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    Do you happen to have a ScanGauge, or any of the various OBD-II reading smartphone apps, that can show you a tachometer so you see how high the engine is revving?

    Are you writing about the engine revving higher than normal powering down the road, or just idling higher? Normal idle for it is around 1000 to 1100 or so.

    If you could see the revs, maybe you wouldn't think it was idling as high as you were thinking.

    If your only concern is at idle, is it possible what you're really hearing is the electric cooling fans coming on?
     
  3. Kusumar

    Kusumar New Member

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    It’s revving high when I’m driving. When I accelerate, the revs doesn’t drop down until a few seconds later. There’s like a rev hang happening. Revs at idle is fine
     
  4. bisco

    bisco cookie crumbler

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    maybe the battery is getting weak, how many miles on her?
     
  5. Mdv55

    Mdv55 Active Member

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    Two factors that can effect this the most are main battery condition and A/C system condition. If your battery is older you're more likely to notice "changes" in sounds and behavior. If your A/C is not properly charged the system is going to work harder which is going to mean more power usage and you're also going to notice the engine working more to move the car/maintain battery SOC.

    Heavy A/C use rips through the battery pack. If the A/C is running at 2000 watts and pulling 8-9 amps your pack is going to discharge fast. I've noticed if I'm in heavy traffic or lots of stop and go city use the engine is almost running to help keep the pack charged. If I can't use regen braking enough the pack will actually discharge faster then "normal" driving will help keep it charged.

    Discharging fast/low battery levels also means the engine is providing more tractive power and sounds labored while the car feels sluggish in comparison. I'll actually lose 10mpg in some areas since the engine is either always running to keep the pack charged or just hauling the car around without a lot of assistance from the hybrid side.

    This behavior changes immediately once the car can stay moving more and maintains a higher state of charge. These cars just operate different from what we're used to as well.
     
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