Uncommon cabin heat problem

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by VicTaxi18, Dec 6, 2014.

  1. VicTaxi18

    VicTaxi18 Junior Member

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    2009 Prius
    The climate control system in my 2006 Prius works just fine at the first start of the day for a few minutes. Then it shuts off for a second or two. Then it turns on for about three seconds. And then off again. Over and over. The MFD shows the system go off and back on. The dash lights for auto or defrost go on and off with the fan as well. The ICE will cycle on and off with the heater when at a stop once the engine is warm. If the rear defroster is on it gets cancelled with every cycle of the climate control. If the climate control is off, the rear defroster works normally.

    This car is a taxi. It recently had an accident with a deer and the hood, front bumper and right headlight assembly had to be replaced. Other than this problem the car doesn't currently have any quirks. A couple of years back the same car intermittently shut down while driving and wouldn't go back into ready mode without clearing the codes. It spent a week at my regular shop and two weeks at a dealer. Neither could figure out that problem, which by then was regularly happening within 15 minutes of a start. Then the problem mysteriously disappeared and the dealer told me to take it away. That problem hasn't reoccurred.

    I've had the car at my regular shop twice and at the dealer for three days to deal with this problem. No success. The blower motor was replaced. Relays were replaced. The MFD, the AC Thermistor and the AC Amplifier were swapped out. I swapped out the Blower Fan Controller. Nobody has seen any sign of damaged wiring. I am told that water pumps are working fine. The dealer tells me that he can't go further until I take all the taxi equipment out of the car.

    So the car is back in service and we get barely enough heat to get by. And it's kind of like sitting beside someone who is about to sneeze all day with all the on and off of the motor and the fan. All that starting and stopping has to be tough on the ICE. What should I do next?
     
  2. valde3

    valde3 Senior Member

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    Diagnose it correctly. If you want to do it yourself get techstream and do tests for the system. If not only option is to get better shop… Why taxi equipment needs to be taken out by of the car by you?
     
  3. bisco

    bisco cookie crumbler

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    how many miles on her? could the outside temp sensor behind the gripe affect the hvac?
     
  4. VicTaxi18

    VicTaxi18 Junior Member

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    Car has 200-300,000 miles on it, The only outside temperature sensor that I know of is between the grille and the rad. I drive that car tomorrow and I'll pay attention to whether it is reporting temperature correctly then. It was showing the 'near freezing' light in the dash today which is a little weird now that I think about it because it's about 10 degrees Celcius now in the evening and that normally only comes on at about 3 degrees Celcius.
     
  5. VicTaxi18

    VicTaxi18 Junior Member

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    Techstream is a possibility. I don't think there is a better shop short of driving 10+ hours to SF. Toyota dealer here is flummoxed but they can access some kind of help from Toyota on the East coast. Those people insist that they will only deal with a car that has no aftermarket equipment in it. I could take the taxi stuff out if I have to and reinstall after. That's just money and time but it would give me a chance to clean up the install. It's quite the mess. On the other hand I think the dealer will not be happy to see this car come back with the same problem. Hmm.

    Both those options are workable. I'm still tempted to try swapping out stuff though. Body ECU? Inverter? Disable coolant thermos system?
     
  6. nh7o

    nh7o Off grid since 1980

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    No, that pertains to doors and lights mainly.
    Eeek. No.
    That will give you a check engine light. It is not the culprit.

    I would pay attention to that temp sensor. Given the accident history, it could be intermittent.
     
  7. valde3

    valde3 Senior Member

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    Don’t do that. Shops have already proven that that’s not good way. Diagnose it or get somebody to diagnose it correctly.
     
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