A/C Compressor Issue

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Laith.khresheh, Apr 24, 2021.

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  1. Laith.khresheh

    Laith.khresheh New Member

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    2011 Prius
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    2011 Prius with 100k miles.

    So here's the issue... The HVAC unit stopped blowing cold air after replacing the heater core unit (dash disassembled) and the A/C compressor is not running.

    All fuses and relays have been checked.

    Held down the climate control system ''AUTO'' and ''FRESH/RECIRC'' buttons and code number 23 came up.

    I've also scanned the ECU for trouble codes:

    - B1423 "Open in Pressure Sensor Circuit/ Abnormal Refigerant Pressure".

    - U0164 ''Lost communication with HVAC Control Module''.

    I'm worried that there's a short circuit in the CAN system with regards to code U0164.

    Appriciate your input regarding the above issue before going to the repair shop ''gussing work''.
     
    #1 Laith.khresheh, Apr 24, 2021
    Bohemian Grove likes this.
  2. ChapmanF

    ChapmanF Senior Member

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    Who replaced the heater core? That's an extensive disassembly, lots of chances to forget a connection or something. Was the refrigerant reclaimed beforehand and, if so,was the A/C properly recharged?
     
    #2 ChapmanF, Apr 24, 2021
  3. Laith.khresheh

    Laith.khresheh New Member

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    Thanks for the prompt reply.
    The heater core was replaced by a local repair shop and the refrigerant was properly charged after the disassembly. Could a loose connection be the culprit of U0164 code?

    I've tested the resistance on the DLC3(OBD2) port and here are the results:
    - CANH to CANL => 60 Ohms (in the specified range)
    - CANH to CG (Ground) => Zero Ohms (Should be 200 Ohms or higher)
    - CANL to CG (Ground) => Zero Ohms (Should be 200 Ohms or higher)

    Does the above results indicate a loose connection or a short circuit?
     
    #3 Laith.khresheh, Apr 24, 2021
  4. ChapmanF

    ChapmanF Senior Member

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    Something is suspect about your technique here. If there is a zero-ohm path from CANH to CG, and there is a zero-ohm path from CANL to CG, then there is a zero-ohm path from CANH to CANL, contradicting your first result.

    Is it possible that the meter display you are calling "zero ohms" in result 2 and 3 is in fact the reading your meter displays for resistance overrange? That would be the expected result, and would satisfy the "200 Ω or higher" criterion.
     
    #4 ChapmanF, Apr 25, 2021
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