AC stops working at slow speeds in traffic

Discussion in 'Prius c Care, Maintenance and Troubleshooting' started by PriusCamper, May 31, 2026 at 5:18 PM.

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  1. PriusCamper

    PriusCamper Senior Member

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    In the 2013 Prius C owner's own words:

    "Today while in very slow traffic we had the same problem as I'd been concerned about last summer: the car overheat warning light comes on when running the AC while driving slowly (about 6-12 mph). The AC worked when we were going over 8 mph but not so much while traffic was stopped. Interested to hear what you think might be going on."

    I did 100K mile work on this Prius C last week with new spark plugs, clean out of the intake system, oil change, etc.. And driving the car home 15 minutes and back the AC worked fine. Engine coolant reservoir was low, but not much and just a tiny bit low under radiator cap.

    The problem evidently existed before front end damage led to a bodyshop replacing the condenser. Also the useless idiots at Toyota Stealership looked at it in Winter and said system had leaks and needed everything replaced, which makes no sense because AC works fine other than when things heat up and car drives slowly.

    Back in the day there were Auto AC specialists, but these days it seems only regular auto shops are the only option, but the most trusted shop in town charged a friend who owns a Honda Hybrid $125 an hour to give her the same BS routine of detecting minor leaks after charging the system and more than a year later her AC is still going strong. Seems like detecting minor leaks is the standard operating procedure for charging people a fortune these days.

    Anyone got any advice?

    Any sense of what's wrong?
     
    #1 PriusCamper, May 31, 2026 at 5:18 PM
    Last edited: May 31, 2026 at 5:30 PM
  2. PriusCamper

    PriusCamper Senior Member

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    #2 PriusCamper, May 31, 2026 at 5:36 PM
  3. ChapmanF

    ChapmanF Senior Member

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    There are electric fans under the hood (fans? I don't know how many are in a Prius c, but the bigger Prii all have two of 'em, as far as I know) to make sure enough air keeps flowing through the condenser and radiator when you are stopped or moving slowly.

    Are you positive the fan(s) work?
     
    #3 ChapmanF, May 31, 2026 at 6:14 PM
    Tombukt2 likes this.
  4. Tombukt2

    Tombukt2 Senior Member

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    So you're saying that going below the 6 mi an hour the airs getting warm etc . Are the radiator fans running just out of curiosity? this is replaced condenser? You know there have been some issues with some condensers . Like these sort of things . Something about internal. Of the core how it's made .
     
    #4 Tombukt2, May 31, 2026 at 6:16 PM
  5. Tombukt2

    Tombukt2 Senior Member

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    What do the gauges say if you hook up gauges to the system both gauges high and low what do you see thru the cycles any high readings that collapse etc . To me it sounds like you've got a metal line that's very crimped you got a serious flow issue . Seems like . We have a cold fat silver line and a warm skinnier line ?
     
    #5 Tombukt2, May 31, 2026 at 6:18 PM
  6. PriusCamper

    PriusCamper Senior Member

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    We haven't got to the gauges yet... But now that I think of it the horn wouldn't work and I fixed it last week by checking the fuse and connectors and got it working just by cleaning and inspecting so I'll do the same for the fan. I wonder which fuse is coolant fan? The diagrams you can find online for "Prius C" fuseboxes never seem to show the correct one...

    Prius C is such an odd car and no longer in production. It's amazing how many things were designed differently for such a short production run. I always thous the Yaris looked nicer than the C, but no Yaris hybrid in the US.
     
    #6 PriusCamper, May 31, 2026 at 7:31 PM
  7. rjparker

    rjparker Tu Humilde Sirviente

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    The poor customer is telling you what the problem is; the engine is overheating. Solve that first and the ac will be ok; ok but not great since it has a slow leak.

    First, if the engine or inverter cooling system is overheating, the ac will be disabled.

    Second, if the engine or inverter does not overheat while moving faster than 12 mph, it sounds like the engine has to continue running and the radiator fan(s) are bad. If the engine does not stop at low speeds it also has a weak hv battery. Probably some off brand aftermarket hv battery.

    Finally, the ac system has a txv refrigerant metering system which will compensate for some degree of low refrigerant. Until its almost gone or there is a very high cabin heat load.
     
    #7 rjparker, May 31, 2026 at 7:35 PM
  8. ChapmanF

    ChapmanF Senior Member

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    I find the c a very cute car, plus they put better colors on it than the liftbacks got. I still make an aww face every time I see one. If I didn't occasionally carry bigger stuff, I'd probably be driving one.

    I spotted one last night with quite nice-looking wheels, but I didn't take a picture on my way into the place, and it was gone by the time I came out.
     
    #8 ChapmanF, May 31, 2026 at 7:35 PM
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