A/C Amplifier Location

Discussion in 'Gen 2 Prius Technical Discussion' started by jerlands, Jun 7, 2019.

  1. jerlands

    jerlands Member

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    Can someone tell me how to access the A/C Amplifier?

    The A/C is not working properly (intermittent) and the steering wheel climate control isn't working (which I whack-a-mole'd.) apparently I can test the amplifier once I get there :)

    EDIT: The new control pad now seems to be working (and apparently so does the A/C?) but I'd still like to know how to access the A/C Amplifier?
    Now anyway I can run the diagnostic (if I understand how to do that correctly :)
     
    #1 jerlands, Jun 7, 2019
    Last edited: Jun 7, 2019
  2. sam spade 2

    sam spade 2 Senior Member

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    What exactly is an A/C "amplifier" ??
    Never heard that term used before.
     
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  3. ChapmanF

    ChapmanF Senior Member

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    It's the ECU responsible for running the HVAC. Called 'amplifier' for hysterical reasons. It's kind of responsible for amplifying some temperature signals and using them as feedback in a control loop. Used to be done in all kinds of clever analog ways, such as pneumatic. Now it's a digital microcontroller like everything else, but the name persists.

    I could tell you right where it is in Gen 3, but not sure about Gen 2; check the parts diagrams or EWD.
     
  4. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    On the Gen 2 the A/C CPU is on a board near the bottom of the Inverter.
    [​IMG]



    This video covers all the High Voltage parts, the A/C system starts at 15:05 to 16:55.
     
    #4 JimboPalmer, Jun 8, 2019
    Last edited: Jun 8, 2019
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  5. jerlands

    jerlands Member

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    The location of the amplifier seems to vary with generations but I now have the AC service manual and apparently it's easily accessed by removing the "instrument panel finish panel lower center." Which seems to imply the rounded cover panel bringing the dash to the floor.
     
  6. jerlands

    jerlands Member

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    The AC just isn't working right... I cleaned the condenser, had the refrigerant evacuated, weighed (thinking it might be overcharged) now am searching out possible control issues. I ran the on board AC diagnostic which firstly returned "diagnosis 43 and 21" but after clearing and retesting only 21 remained (I was in shade.) Oddly though I found the old control pad to be good but which doesn't explain why I was unable to get any of the climate control buttons to function earlier. Apparently this is intermittent and so might be something like the spiral cable but I'm preparing myself the the amplifier. I know where it is now and just have to take the time to look further into it.

    I also ran all active ac tests in Techstream and recorded the response of each which all looked ok with only one deviating about 2.5% consistently lower than the signal throughout the test.
     
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  7. ChapmanF

    ChapmanF Senior Member

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    That's just the high-voltage circuitry inside the inverter that makes the 3-phase AC waveforms that spin the A/C compressor.

    The A/C amplifier is just another ordinary low-voltage microcontroller, deciding when to do things like move the flaps, run the pump, tell the compressor circuit what speed to run, and so on. It's callout 88650H, here:

    [​IMG]
     
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  8. TMR-JWAP

    TMR-JWAP Senior Member

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    I'll just throw this out there, just in case.....

    I have seen intermittent AC problems be caused by intermittent inverter cooling water pump failure...
    Many times weird AC issues are the first indication the ICWP is having problems.
    Nothing worse than dumping a bunch of money into an AC system, just to find out it's a $65 pump....
     
  9. jerlands

    jerlands Member

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    I replaced the pump about 4 months ago and also just recently replaced the HV battery. The things I noticed weird during the period my battery was failing is the way it behaved going downhill (I'm in the Sierra's) when the battery charge was full and in B Mode it would send too much current to MG1 and too suddenly because the engine would wind out terribly (I would always then switch to D Mode.) That now doesn't happen with the new (rebuilt) battery. I also totally lost power just before I replaced the battery. I originally thought the vehicle had sped up but I now think it went to neutral because I saw no activity from battery (charging or discharging) when I felt the speed change (I was going downhill almost entering the incline.) I shut off power, let it sit for maybe a minute, turned it back on and was able to get on my way.

    I've been driving the vehicle for about 8 mos. and have known about the AC issue from the beginning so if the two are related seems possible. The AC seems to be working fine now for whatever reason :)
     
    #9 jerlands, Jun 8, 2019
    Last edited: Jun 8, 2019
  10. jerlands

    jerlands Member

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    The image seems to show where I understood it to be but I'm not certain how to access it? Seems just behind the rounded finish panel between the dash and the floor?
     
  11. ChapmanF

    ChapmanF Senior Member

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    Do you have access to the Repair Manual? I'd expect instructions to be in there for what panels to remove in what order, etc.
     
  12. edthefox5

    edthefox5 Senior Member

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    My 07 Manual shows the 2 AC Control ECU's (A7 & A8) mounted on the floor behind the plastic center foot cover right under the radio.
    The big plastic cover under the dash between the seats. If you opened the center console secret bottom drawer it almost hits the cover I am taking about.

    Some questions:

    Is this a salvage car?
    Whats the behavior of the cooling fans behind the condenser when ac turned on & off.
    Has the refrigerant ever been changed and is it the correct ND refrigerant? Its uses special refrigerant.

    And DTC codes for the ac system are B codes as in BXXXX.
     
  13. ChapmanF

    ChapmanF Senior Member

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    When you get the codes by asking the HVAC system itself (holding AUTO and RECIRC while powering the car on), they are shown as two-digit codes on the MFD (21 = B1421, etc.).

    Wiring diagram designations like A7 and A8 refer to connectors; in this case there are two wiring harness connectors that plug into the AC 'amplifier' ECU.
     
  14. edthefox5

    edthefox5 Senior Member

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    That's nice there still where I said they were and gave him that connector info for future reference if he gets a manual. But thanks for busting my balls again.
     
  15. ChapmanF

    ChapmanF Senior Member

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    ?

    PriusChat threads stay around a long time. People will come along years later and read them looking for information. If something looks like it might cause confusion to either the current OP or to some future reader, I try to leave it straightened out. I'm not out to make it personal most of the time, and nothing I was seeing in this thread seemed to call for it. Sorry if it seemed like I was out to get you.
     
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  16. jerlands

    jerlands Member

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    Thank you... that's what I thought... I just have to pull it off I think :)
    Yes, I don't know the specifics but it looks like it took it on the front, drivers side.
    I've been under the car once where I had a good look at this and both fans were running with the AC on but I didn't cycle them (just me.)
    I understand about the refrigerant using special oil... In the past I believe they added refrigerant... I had the system evacuated, weighed, and put back and I told the guy who did it all about it being a hybrid and who seemed to know where some fuse was in the engine bay box but if what he had in his recovery unit wasn't right with mine then I'll be having other future problems. I have been smelling something like an overheating electronic part.
    The codes I got were B1443 (Air Outlet Damper Control Circuit) and B1421 (Solar Sensor)
    I cleared the codes, retested and B1443 cleared but the sensor didn't I believe because I was in the shade.
     
  17. edthefox5

    edthefox5 Senior Member

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    I suspected a salvage we see alot of that here and usually are difficult to diagnosis.The ac system in a G2 really works well and usually does not have many issues other than man made.Going on 13 years omn mine never an issue on full blast everyday.

    I recommend you take it to a ac shop. Ask them the minute you walk in if they know about G2 prius. I am lucky around here theirs lot of ac shops and they know G2's very well its a very popular car. If it was me I would do a full evac and then charge with dye and let them do there thing. The fact that the fans are on tell me the ecu is working ok they command the fans. In AC HIGH both fans should be at max speed and make sure they are not on backwards thats a common issue they both should be sucking not blowing. See lots of backward fans.

    Good luck. AC issues are hard and best left to the pro's.
     
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  18. jerlands

    jerlands Member

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    backwards fans??? that almost sounds a possibility cause it seems to cool better at higher speeds... I'll see if I can catch the rotation and try and figure out which way it should be going to pull air to pull air through the radiator...
    edit: I guess I could stick something down there and see which way it's blowing :)
     
    #18 jerlands, Jun 11, 2019
    Last edited: Jun 11, 2019
  19. jerlands

    jerlands Member

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    The only problem I'm having in all this without going out and testing is my steering wheel climate controls went out again... so... one thing at a time :)
     
  20. edthefox5

    edthefox5 Senior Member

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    yes thats classic sign of backwards fan. Cools off when driving spikes when sitting at light. I have seen a few salvages here with front end damage they put the fan on backwards. Just put your hand behind it should be blowing on your hand.

    And clock spring is fun.
     
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