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A/C Blower Fan trips Master Warning Light

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by yortlecti, Aug 31, 2016.

  1. yortlecti

    yortlecti Junior Member

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    Hi all,

    I have been a long time lurker, and gained invaluable information from the PC masses, for which I humbly thank you. I have now come up against an issue that I can't seem to locate a solution for. I outline it below, in the painstaking detail I expect those who offer an opinion will expect:

    I purchased my 2006 Prius in April of this year, putting it squarely at 10 years old. It had 128,000 miles. I got it from an auto-auction for a song and a dance. Day 2 of ownership and my MWL trips upon starting the vehicle and cranking the heat. I immediately freak out and start kicking myself for being so stupid. After reading the various articles on here regarding the 12v battery failure, and those symptoms, I decided to swap the existing battery (which, it turns out was a $20 lawn mower battery from Wal-Mart. I kid you not.) for an Optima Yellow Top. All is well, the MWL is cleared, and I go on my merry way.

    Not long after this, I hop in the car, put it in READY, and fire the heater up again. Same as before, MWL and a few other lights trip (not the Check Engine, though) and my freaking out begins all over. This time, I was equipped with an OBDII scanner and Torque Pro. I pulled the codes and, surprise, there were none. I cycled the car to READY and back again around 5 times, and all the lights reset.

    Over the past 4 months, this cycle has repeated multiple times, and every time it is triggered by pushing the A/C or Heat blower beyond the halfway point (above half power). I've tried pulling the codes using Torque Pro multiple times, with no luck. I usually just cycle the car on and off until the lights clear, but I understand that's a temporary solution. I am now looking at reselling the car and purchasing a 2010, so I need to have an answer to provide to the next buyer (if it's not something I can fix myself, that is).

    There are NO other symptoms. I've driven multiple Prius (I've sourced 4 or 5 for friends and family after they saw the savings I was experiencing by driving mine) and know what to expect; mine behaves appropriately, apart from protesting the use of the cabin air blower on a high setting. I'm sure this is an easy diagnosis for some of you, but I'm stumped. I am at the mercy of your generosity and wisdom.

    Thank you all for your time,

    Michael
     
    #1 yortlecti, Aug 31, 2016
  2. bisco

    bisco cookie crumbler

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    welcome and congrats! could it be that the motor is worn and pulling too many amps? i would pull it out and have a look see for debris as well. have you already changed the cabin air filter?
     
    #2 bisco, Aug 31, 2016
  3. yortlecti

    yortlecti Junior Member

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    Thanks for the welcome! It didn't occur to me that it would pull more amps when it is worn, I guess I just expected it to die instead. I haven't pulled the blower motor, and come to think of it, I didn't swap the cabin air filter like I meant to either. Could this really be the nemesis?

    Posted via the PriusChat mobile app.
     
    #3 yortlecti, Aug 31, 2016
  4. jdcollins5

    jdcollins5 Senior Member

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    If you are calling the MWL the red triangle then there will be a DTC triggered. Torque Pro cannot read the Prius specific DTC's from the multiple ECU's. You will need to get something like a laptop and mini-VCI to read the DTC's. This will tell you what is triggering the MWL.
     
    #4 jdcollins5, Aug 31, 2016
  5. yortlecti

    yortlecti Junior Member

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    Yes, the red triangle is what I am referring to as the Master Warning Light (MWL). I apologize if my terminology is incorrect. I was able to pull a P0012 from my buddy's '06 Prius when his Check Engine light tripped, I'm assuming that isn't a Prius-specific DTC? I may have to invest in the mini-VCI (unless there are any PC members in the Toledo area who'd be willing to meet up with me).I'm hoping I can find someone on here who has experienced what I'm talking about.
     
    #5 yortlecti, Aug 31, 2016
  6. ChapmanF

    ChapmanF Senior Member

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    Hmm.

    There's a little-known known Prius fact that is so well buried it hardly ever gets mentioned even here on PriusChat.

    Built into the heater, you also have somewhere in the neighborhood of 700 watts of electric heat elements. They only come on if you crank the heat early, before the engine coolant is warmed up. When they do, it's a sizeable electric draw (sixty amps or thereabouts).

    That, combined with the draw of the blower motor itself (smaller but still respectable, on high) could be putting a substantial draw on the DC/DC converter ... more so if you're getting started before it's light, and using the headlights, etc. I wonder if you're getting a converter code (and not seeing it because Torque doesn't have a definition for it).

    Can you trigger the warnings any old time you turn the blower up high, or does it happen more in cold temps, before the engine is warm, when the electric heat might come on?

    How does the flow of inverter coolant look, if you look into the reservoir with the ignition on?

    -Chap
     
    #6 ChapmanF, Aug 31, 2016
    jdcollins5 likes this.
  7. jdcollins5

    jdcollins5 Senior Member

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    The Torque Pro will give you the standard engine and emission DTC's when the Chech Engine Light comes on but not Prius specific DTC's from the HV Battery, etc. that trigger the MWL. You will need something that can read Prius specific codes from the multiple ECU's (electronic control unit).

    Chap may be on to something above.
     
    #7 jdcollins5, Aug 31, 2016
  8. ChapmanF

    ChapmanF Senior Member

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    Might be worth checking (hunt around the forum) for custom PID definitions you could load into Torque to read more Prius-specific data. When I was driving a Gen 1, I remember Vincent worked out the PIDs to retrieve codes from the HV ECU, I added those in my ScanGauge.

    -Chap
     
    #8 ChapmanF, Aug 31, 2016
  9. yortlecti

    yortlecti Junior Member

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    I appreciate the guidance. I do have Torque Pro loaded with the latest PIDs provided by usbseawolf2000, but I'm not sure that includes Prius-specific DTC's. I will continue hunting, and if anyone beats me to finding them, I'd sure appreciate a steer. Thanks to all for the input!

    Posted via the PriusChat mobile app.
     
    #9 yortlecti, Sep 1, 2016
  10. yortlecti

    yortlecti Junior Member

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    I have no idea how I missed this post, sorry for the delayed reply. I have been able to replicate this under both hot and cold conditions. The first time was on an early April morning, and yes, the headlights and other power draws were at play as well.

    Over the summer, I encountered the same issue if it was too hot. Kicking the A/C on in and of itself doesn't cause the problem, but cranking the blower above the middle setting will trip it. Under milder conditions, I haven't had an issue, even with putting the blower on high. That may be due to other variables, though.

    I'm familiar with the inverter pump recall, and not sure if this one has been replaced or not. I do see turmoil in the inverter reservoir when the vehicle is READY. Is your suspicion a bad DC/DC Inverter?

    Thanks again for the input!

    Posted via the PriusChat mobile app.
     
    #10 yortlecti, Sep 1, 2016
  11. ChapmanF

    ChapmanF Senior Member

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    Well, my suspicion is that you really should read the codes; there is probably one in there just waiting to tell you what's going on.

    You might even learn something by asking the HVAC controller for its codes; you don't need a tool for that, just hold AUTO and RECIRC on the steering wheel simultaneously while you put the car IG-ON ... then look for any two-digit codes in the corner of the MFD.

    No guarantee that'll tell you anything, but it's easy to try.

    -Chap
     
    #11 ChapmanF, Sep 1, 2016
  12. yortlecti

    yortlecti Junior Member

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    Genius! I'll give that a whirl. I had loaned the car to a friend for a couple months and just got it back today. Now, I can't replicate the issue. I will give the HVAC codes a try. Any chance you have the interpretation if I actually find something?

    Posted via the PriusChat mobile app.
     
    #12 yortlecti, Sep 1, 2016
  13. ChapmanF

    ChapmanF Senior Member

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    Well, I would just go straight to techinfo for information like that, but I let my days run out, so it would cost either one of us $15 (for the minimum, 2-day access period) to look it up. I tend to sort of save up things I'm wondering about until I have enough to spend $15 on, then just look them all up. When I first bought my Gen 3, I did pop for the $75, full-month option, and got kind of spoiled with a whole month looking up anything I wanted. :)

    There is one code that's worth knowing because it's usually a false alarm, the "hey, there's no light on the solar sensor" code (21 or 24, if I remember right), because you always get it if you check the codes in low light ... it's only a problem if you're seeing strong sunlight hitting the sensor on the dash and still getting the code.

    (That's also an easy way to make sure you're doing the right steps to read the codes; if nothing but 00 is coming up, throw a towel over the light sensor and see if you can get a 21 or 24.)

    -Chap
     
    #13 ChapmanF, Sep 1, 2016
  14. yortlecti

    yortlecti Junior Member

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    Excellent, thanks a ton, Chap! I'll experiment with it tomorrow and report back. If I get an error code, I'll probably dish out the $15. If so, I'll let you know and I'll gladly look up anything you've been stockpiling!

    Posted via the PriusChat mobile app.
     
    #14 yortlecti, Sep 1, 2016
  15. yortlecti

    yortlecti Junior Member

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    Just a quick update, I did query the HVAC system and it only returned "00"...so the hunt continues. The car is out on loan again, but I'll be swapping the cabin air filter when I get it back. Not sure that will help, but I much prefer starting with cheap solutions and working my way up!

    Thanks again for the input.
     
    #15 yortlecti, Sep 6, 2016
  16. bisco

    bisco cookie crumbler

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    when you take out the old cabin filter, the blower fan is right below it. make sure it's clean and spins easily.
    you can start the car and start the fan while it's open, but don't put your fingers in there!
     
    #16 bisco, Sep 6, 2016
  17. yortlecti

    yortlecti Junior Member

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    Good to know! I'll scope it out while I'm in there. Is that part relatively easy to swap out if it's bad, or does it require further dash disassembly?

    Posted via the PriusChat mobile app.
     
    #17 yortlecti, Sep 6, 2016
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