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No Heat; Stuck in Recirc Mode; Occasional Master Warning Light

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by toyoprius, Mar 22, 2009.

  1. toyoprius

    toyoprius New Member

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    This just started today. It's still cold up here in New England, and I noticed that the Prius was blowing cold air with the air conditionioning system set on auto and 68 deg. The recirculation indicator was illuminated, but neither the climate page on the MFD or the steering wheel button could turn it off. I tried "rebooting" the Prius and it did no good.

    On the way home tonight, the Master Warning Indicator illuminated for five seconds or so, and then went out.

    No heat, air recirc always on, occassional Master Warning Indicator: Any ideas? Thanks!

    Karl
    2004 60K miles
     
  2. jayman

    jayman Senior Member

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    Karl

    There should be a specific code set. Otherwise your only option is to check the basics - eg fuses - and then begin a process of elimination

    jay
     
  3. toyoprius

    toyoprius New Member

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    Thanks, Jay. It didn't throw any codes.

    This is a little frustrating. In a normal car, I'd sort of know where to start. Or at least I'd know who the usual suspects were if the heater stopped. In the computerized marvel, I'm clueless. I am also wondering why the master warning symbol briefly illuminated while driving. In the six years I've been driving this Prius, that has never happened.

    It's locked in recirculation mode, which I suspect is just a symptom of the underlying problem.

    If anyone has any other ideas, I'd love to hear them. Otherwise, it's probably off to the dealer.
     
  4. jayman

    jayman Senior Member

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    If the Triangle of Doom turned on, a code *should* be stored. Keep in mind that proprietary Toyota codes cannot be read by generic OBD II scanners.

    You'll probably have to pay a Toyota shop to plug in their Panasonic ToughBook - with CAN dongle - to read everything

    A 24 hour subscription to Toyota TechInfo is around $10. A yearly subscription to All Data DIY is around $16, and appears to offer most of the Toyota content, including current TSB's

    I'm going to research this further but am busy right now. Expect to hear back in 24 hours
     
  5. qbee42

    qbee42 My other car is a boat

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    The 12V system is always a suspect when a Prius does weird things. If you don't find any other problems, it's worth a look at the 12V bus voltage.

    Tom
     
  6. Rokeby

    Rokeby Member

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    Just a thought...

    Does the A/C system CPU/ECU know if the cabin air filter is clogged?

    As the HV battery is ultimately cooled/heated by cabin air, could a really
    clogged filter be a condition that would restrict air flow to recirc?
     
  7. jayman

    jayman Senior Member

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    No, it doesn't know if the filter is plugged. It's easy enough to remove the glovebox and check on the cabin air filter.
     
  8. toyoprius

    toyoprius New Member

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    The air filter was the first thing I checked. Not as a result of a brilliant line of reasoning, just because I couldn't think of anything else to look at.

    "Recirculation on" might be a red herring. I wonder if the heating system works similar to the A/C--if the differential between desired temperature and actual temperature is over a certain threshold, the system shifts to recirc? I just never recall seeing it when the system was calling for heat.

    I knew that if the check engine light was illuminated, you would find stored DTCs. I didn't realize that you'd find a DTC with the red triangle of doom, too. I'll report back when I finally figure out the problem.
     
  9. toyoprius

    toyoprius New Member

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    Epilogue:

    It was simply a bad water pump. The red triangle master which had been very intermittent, finally stayed illuminated. Eventually, a water temperature icon appeared on the MFD.

    The coolant reservoir always showed full so this threw me off track.

    If anyone is getting near the end of their 5 year powertrain warranty, I would check the waterpump for leakage. It's an expensive 3 hour $450 repair. I watched the technician perform the swap, and it didn't look like an easy do-it-yourselfer. Like everything Prius, it's not your grandaddy's waterpump.
     
  10. jayman

    jayman Senior Member

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    Sucks the water pump was bad, but hopefully you got it in time before serious damage was done