No air out of defrost vents at windshield

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by pasadena_commut, Mar 17, 2020.

  1. pasadena_commut

    pasadena_commut Active Member

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    Rainy and cold today for the first time in a long time and there were two damp people in the car. Front window fogged up. Pushed the front defrost button and - nothing. It stayed defrosted. Felt the center vents under the windshield and nothing was coming out there. Tried every position and nada. Eventually with the fan going full bore, the heat cranked up, and the A/C button pressed the front window defrosted (despite the lack of any air flow directly onto it) and it was once again safe to drive. I don't recall ever having used the front defrost before (only owned the car about a year and it isn't cold and wet here that often.) The dealer took the dash apart a couple of months ago to replace the evaporator in the center, possibly they didn't reattach some wire which controls the vent positions? If so, where would that be?

    I have also seen references to an "A/C amplifier" which apparently somehow or other integrates all the sensors. That might also be a problem since the heat has been pretty strange, like so: set it to 68 and it blows cold, set it to 69 and it starts blowing hot. Not quite a binary choice, but very discontinuous in terms of the outlet temperature from the vent. It is also very hard to "make the car blow warm air out the vents" since it depends on the outside temperature in some complicated way. One day it might blow warm at 69, and another it might do so at 65. I had not payed much attention to that, but it was annoying to have to keep tapping the temperature up different amounts to get the same amount of hot air out. (I long for the days when there were no automatic HVAC - it was much easier to twist the heat knob to 40% red, twist the vent knob to defrost, and push the A/C button, and done. No vent motors or electronics involved and more or less foolproof.)
     
  2. bisco

    bisco cookie crumbler

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    unfortunately, most of the components are behind the dash, and it will probably have to be removed again
     
  3. pasadena_commut

    pasadena_commut Active Member

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    Right, Murphy strikes again. In theory the vents were working when the dealer sold it (on the immensely long check list they provided) and it is pretty likely that they just failed to reattach the cable to the unit when they had the dash apart.

    Messed with it a little more this morning. The air cannot be redirected. All positions come out the dash vents, never up, never down. Recirc vs. fresh works (and that unit sometimes makes a little noise when it switches so that one can tell that something is happening). If anybody has a diagram or other information about the "air direction module", or whatever they call it, please post it or a link to it. Thanks.
     
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  4. bisco

    bisco cookie crumbler

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    you can also look in the service manual. maybe some of the connections are accessable
     
  5. pasadena_commut

    pasadena_commut Active Member

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    I will look around for a copy.

    In the meantime the HVAC diagnostic was run by holding the "automatic" and "recirc" buttons when the car was started. It alternately flashed the numbers 42 and 43 and the icons for "vent" (horizontal arrow towards driver) and "fresh air" were also flashing.
     
  6. bisco

    bisco cookie crumbler

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    could just be a stuck door, but that may also require dash disassembly
     
  7. davecook89t

    davecook89t Senior Member

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    You could try this:

    Google Drive - Virus scan warning

    Thanks to @MickeyMatter, I've had his on my hard drive for a couple of years, with no issues.

    There are 26 pages dealing with the "Air Mix Damper", "Air Inlet Damper", "Air Outlet Damper", Manual Pages AC-67 to AC-92, any or all of which might be relevant to your problem, but for each fault you should have a DTC (B1431,B1432,B1433,B1441,B1442, or B1443). Possibly you would only see these using Techstream.

    Edit: Looks like the link doesn't work anymore. I know @SFO often can provide a link to the relevant pages, if he would be so kind.;-)
     
  8. pasadena_commut

    pasadena_commut Active Member

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    I'm looking into this again (there was no urgency since the car has only added 400 miles in the interim and it has been blazing hot for most of that). 21 is the sun sensor, which is irrelevant. 42 and 43 are the input and output selectors and looking at the "what these could be" both include the a/c amplifier and the wiring harness. The amplifier is behind the rounded plastic piece below the radio which connects the dash to the carpet. Is there a video around showing how to take that plastic piece off? Just that piece, not the entire dash disassembly, if at all possible.

    Edit: Found this guide

    http://techno-fandom.org/~hobbit/cars/chris-dragon-dash.pdf

    which shows how to remove that piece (and the radio, but not the whole dashboard.)
     
    #8 pasadena_commut, Sep 22, 2020
    Last edited: Sep 22, 2020
  9. pasadena_commut

    pasadena_commut Active Member

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    So, I tried to get to the A/C amplifier today. Removing the lower center panel on the dash was easy. Pull out the one push pin on the passenger side then yank out the cover straight towards the back of the car. However, the "No. 3 Air Duct" plugs right into a duct directly underneath it and blocks the whole front of the A/C amplifier from view. I tried to pull out the duct but the carpet had a death grip on it. AC-147 has a hint that says to "fold back the carpet" which I fear means fold it back on both sides from the front to the seats. Anyway, after crawling under the dash for a while I spotted the two connectors to that ECU shown on page EC-30. Except they were upside down and the wire colors didn't match, but the pin outs and relative orientation to each other looked the same otherwise. Maybe they recolored the wire harness at some point after the manual was written? Also not being an octopus I could not place two DVM probes on the appropriate spots while simultaneously moving the very stiff cable out of the way, holding down the carpet, and holding a flashlight. Have any of you changed one of these? I can get one for cheap on Ebay and even though getting that duct out may take some work it looks much easier than completely disassembling the dash.

    On a related point, where exactly is the "air outlet control servo motor"? The A/C manual only discusses removing it in the "disassembly" section. That is, after the whole dash has been torn apart, the hoses removed, and the center section pulled out of the car. That ain't happening. I see two servo motor like objects when looking up from the gas pedal. There is a video for removing the "blend door", which I think is the upper one. The lower one has a very complex mechanical linkage (all plastic parts). If that is the correct servo motor I could apply voltages to the two pins that make it move and see if it goes.

    Finally, if one replaces the evaporator with a whole unit does it come with new servos? When the car went in to have that done the outlet vents could be redirected, afterwards, not (although I did not notice it for months, and then we had the pandemic.)
     
  10. pasadena_commut

    pasadena_commut Active Member

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    So, I took it back to the dealer since they say they give a 1 year warranty on their work. They called me back a few hours later and said "it's working" and that the error codes were "stored from when they did the work." So I go back and pick it up. Total bullshit. I reran the diagnostics and 43 is still there (42 is gone). No air out of the vent, as far as I could tell. But I didn't want to spend a lot of time in the car at that point since heaven only knows how many people were hacking away in it. Drove it home with the windows open and parked it for 3 days.

    Today I went out and reran the diagnostics. Same failure, code 43. Cleared the code. Ran it again, same code. "Stored from when they did the work" my a*s. Ran techstream and the "outlet damper" diagnostic. Fingers in defrost vent and move it from -10 to +110. No air out that vent in any position. I want to air it out another day before crawling under the dash but I'm about 99.999% certain that as before the servo will make no noise and the plastic wheel won't turn. I still think they didn't plug it in when they reassembled, but it could be the door on the new unit is jammed.

    I hate dealer "service".
     
  11. pasadena_commut

    pasadena_commut Active Member

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    Took it back, again. This time they had a "service manager" look at it. Surprise, surprise, the servo was not plugged in. They reconnected it and of course now the diagnostics run clean and air will come out of all the vents.

    Here's the really strange part though. On 9/11/2019 as part of the many many trips to get the A/C fixed they replaced the Schrader valve and the low side line assembly. (Their hope being that was the last of the leaks, but it wasn't, they eventually had to replace the evaporator too.) When I picked up the car the TPMS light was warning: it would flash for a while then stay on. (Posted about it here: Best way to hide TPMS warning light? | PriusChat) So before accepting the vehicle I asked them if they had done something. No says they, the battery must just have died, coincidentally while it was in the shop. It's possible, if unlikely, and I never bothered fixing it since we check our tire pressures regularly. Anyway, when I pick up the car again this time the TPMS light is no longer warning! The bulb works, it lights up briefly on start up, but then stays out. So either the battery decided to heal itself on this trip, which is much more unlikely than it having given up the ghost on a prior trip, or they disconnected something in the TPMS system on that earlier trip, and this service manager reconnected it. In any case, there were no comments about it on the service record.
     
  12. ChapmanF

    ChapmanF Senior Member

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    In any procedure with as many fiddly steps as dash removal and reinstallation, it's not even a tiny bit astonishing when some small plug gets left unplugged or the like. It's frustrating, and you would hope at a shop they would have enough cross-checking going on to catch things, but everyone involved is human.
     
  13. pasadena_commut

    pasadena_commut Active Member

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    I'm not saying that taking apart the dash and reassembling does not leave room for error. That's why there are step by step instructions in the manual. It is the sort of thing I might screw up, since working on cars isn't my day job, but not something the enormous shop at one of the biggest Toyota dealers in the country should get wrong. Or if they did happen to screw up on reassembly, it is certainly something they should have caught with the absolute minimum of QC by running the super easy "hold down two buttons and start the car" diagnostic. Especially since the work when this went wrong was to replace the evaporator, a key part of the system that diagnostic tests. And it most definitely is not something they should say they have fixed, returned the car, and not have fixed anything when given explicit instructions that "the outlet servo may not be plugged in" and "the diagnostic shows code 43"! That last part is more in the realm of "fraud" than "incompetence".
     
  14. ChapmanF

    ChapmanF Senior Member

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    I understand the frustration, but honestly, that's just the reason I most often DIY. The guy at the enormous shop at the big dealer isn't just doing my 300 step repair, he's got 3 more of them to do before lunch, and my car isn't his car that he has to trust his loved ones to. He probably started the job all idealistic and sure he was never going to be one of those mechanics, but he's also tired of being snapped at by the boss for taking 5 excess minutes double-checking my stuff.

    Personally, I just find it more calming and probably healthy to take my time and do the work myself than to be continually raging at the way things happen at shops.

    As it happens, those few times I do go in to the dealer for service, occasional recall, or flashing an ECU update, those have gone pretty well, knock on wood. I'm generally going in with a very specific small task, often with the TSB in my hand ("would you please flash this ECU to this revision?") and they understand that I'm not asking them to do anything else, and they've been respectful of that. (I still check the work afterward.)
     
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