A/C: Decode this

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Morph, Dec 4, 2022.

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  1. Morph

    Morph New Member

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    My A/C is not cooling. I'm getting codes 12, 21, 76 during indicator check mode (pushing steering wheel buttons to generate codes on the center console screen, per pg AC-36 - 38 of Service Manual). Other than the loss of cold air, there are no indications of any systems failures (no lights coming up on dash, and no DTC's showing on the OBD-II scanner).

    Brought it to an A/C shop, they said the refrigerant levels were normal, and the issue may be the absence of the ambient temp sensor. The car didn't have one when the AC worked, but for the sake of argument I replaced it. Still no cold air.

    Car has 160,000 miles on it and the A/C had been working perfectly until a road trip up to PA recently (where temps were unseasonably cold compared to FL). The inverter coolant pump was replaced a few weeks prior to the trip.

    As suggested here, I've read through the Service Manual and borrowed the Chilton's Repair Manual from the library. But I can't find these double digit codes translated anywhere. Search results here mention that 21 relates to the solar sensor - normal for that to come up unless the dash is in sunlight, but I still need help with 12 and 76. I apologize if I missed it somewhere, the keywords I've tried have not yielded answers. The purpose of my post is not to diagnose why the A/C isn't cooling - I understand what the likely culprits are and the complexity of the system - I'm just hoping to figure out what those codes mean. Thanks in advance.
     
  2. mr_guy_mann

    mr_guy_mann Senior Member

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    Hello and welcome to PriusChat!

    Ok, looking in the service manual I see that 21 is "shorthand" for B1421. For the moment I would assume that the other two are B1412 (ambient temperature sensor circuit) and B1476 (A/C inverter load system malfunction). It doesn't always work out that way, but I don't see the 2-digit codes in the code lists (there are a couple in the body of the text, but not all of them).

    You might consider reading this thread to look at scantool apps & devices. Several give you codes and data for all systems on a Gen2 Prius, and two have bidirectional controls (to let you command some outputs on & off).

    https://priuschat.com/index.php?posts/3290690


    Posted via the PriusChat mobile app.
     
    #2 mr_guy_mann, Dec 5, 2022
    Last edited: Dec 5, 2022
  3. Tombukt2

    Tombukt2 Senior Member

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    So then before all this started and back in Pennsylvania a few weeks ago or whatever when you had the air conditioner running and it was making cold did the air conditioning system sound like it always did or was it starting to get more noisy.? Today while you're trying to do this I'm assuming you're in a garage out of the sunlight in the dead shade under a tree because you're getting the solar sensor code.? Just curious if you brought the car outside in the sunlight and the daylight out of the garage does this change anything? As far as the air conditioner running? Then went in the sunlight out of the garage if you put the system ready turn the temperature to LO put the fan on medium and the AC button you press and put the yellow bar on above the AC meaning the compressor's activated do you hear the compressor come on even for a second? No then go out and check all the fuses and fusible links that would be the first thing I would do to make certain that all my circuits are capable of delivering power wherever they need to go. It sounds like you have a high voltage problem to your compressor or your compressor's not responding to the high voltage it's getting on the orange cable that's feeding the compressor when it's on you could check that orange plug to the compressor with a voltmeter You're looking for 211 plus volts. If you're getting voltage to that plug with everything turned on as stated then more than likely your compressor has failed or is intermittent. Many times I'll undo the power plug right from the compressor while the cars running unplug it and plug it back up once twice maybe three times sometimes the compressor will come back on and then I'll note if it's making a bunch of racket doesn't sound right when it does come on I check the pressures on high and low side and see if I'm around 30 and 200 low and high things like that sounds like you have a serious power problem to the compressor.
     
  4. ChapmanF

    ChapmanF Senior Member

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    Yeah, it's weird that the Gen 2 manual doesn't use the B1421/21 style of listing where the two-digit code follows the slash. And the Gen 1 manual didn't either, because its A/C amplifier didn't do DTCs, and only had the two-digit codes.

    The Gen 3 manual does use the B14xy/xy format, though, and yes, all of its B14xy codes have two-digit codes that match the xy (except for B14A1 and B14A2, for obvious reasons). And they don't seem to shift the meanings around much between generations. (Gen 1 didn't have an electric compressor, though, so no 76 code.)

    So B1412 indicates an open or short in the ambient temperature circuit (which is wired, as it happens, to the ECM, which reads the sensor and sends the reading to the A/C amplifier). There are five pages of troubleshooting steps. If the data list shows an ambient temperature of −23.3℃, that would suggest an open circuit, while 65.95℃ would indicate a short.

    B1476 indicates the compressor was drawing either more or less power than expected for the conditions. That can happen because the refrigerant is overcharged or undercharged, or the condenser fans aren't running when needed (or something else is restricting airflow over the condenser), or there is an issue with the compressor itself. There are a couple pages of troubleshooting steps.
     
  5. Morph

    Morph New Member

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    Is it safe to disconnect/test/reconnect this plug while the car is running/on?

    Thanks for the responses so far, I suspect the compressor as well - it was making more noise than usual after the repair to the inverter coolant pump. I've checked the fuses and connections - no issues there. I have tested the A/C both in the garage and outside, and while driving

    Regarding the codes, if the two digit codes from the indicator check mode do indeed correspond to the last two digits of a DTC, wouldn't those DTC's come up when I scan from the OBD-II/DLC3 port? I will check the link you sent also, and perhaps try a different app with my bluetooth OBD adapter.
     
  6. mr_guy_mann

    mr_guy_mann Senior Member

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    Different app and likely different device. Most are limited in what ecu's they can communicate with, either because the software of the app doesn't cover that system, or because the device is physically unable to connect to that data bus (network).

    Posted via the PriusChat mobile app.
     
  7. ChapmanF

    ChapmanF Senior Member

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    NO!

    That plug should be handled with the car off, preferably the service plug removed, and several minutes elapsed since the power was on.
     
  8. Tombukt2

    Tombukt2 Senior Member

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    Yep that's the best way to handle it as above. But in my Gen 3 it's a plug so I just push the tab and unplug it and left it hanging when I was having air conditioning problems as long as it has a tab that you press to unplug it to me it's safe to do so no matter how many hundreds of volts are behind the plastic to the spades. But that being said when talking to general people they should have the car turned off and the service plug undone because they're regular people not in the know. But for myself I unplugged the compressor while I have the hood up with one hand even touching the hood leave the plug dangling maybe take my test meter on the hi volt scale and see what they're 200 plus volts etc . Can my compressor even possibly run if it was brand new with the voltage coming out of the plug? If so reinsert the plug maybe turn on the compressor. Also the six-prong plug on top of the compressor is what's going to do the switching of that high voltage inside the compressor from onto off up and down etc so there could be control issues which I guess is common in these heavily ECU controlled compressors. Getting noisy and making a racket at last use can be a good clue. I can unplug my 30 amp dryer at my house dryer running or off pretty uneventful I would think it would be similar with the reverse spade type of plug used that I'm looking at on my compressor anyway. If I disconnect the orange plug and do all that to unplug the plug at the compressor then to test the voltage at that compressor plug I now have to go back and replug the orange plug the safety thing reboot the car etc etc when I was having this problem all I did was slide the plug loose leave it dangling in the car check the voltage at that plug with the air switches and all the proper positions and make a note that I had voltage very quickly and that my problem was further up the line compressor or controls
     
  9. ChapmanF

    ChapmanF Senior Member

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    Another thing to be "in the know" about would be the differences between Gen 2 and Gen 3. It's a plug, in both cases, but in Gen 3 it's a two-wire plug that simply brings DC power to the compressor. The inverter circuit that runs the compressor motor is inside the compressor itself.

    In the Gen 2 (this thread's in the Gen 2 forum), it's a three-wire plug that brings three-phase AC to the compressor motor, coming from the outputs of the variable-frequency motor drive circuitry inside the inverter box, and those are the circuits you'd be interrupting if you went playing with the plug while powered up.
     
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