2010 Prius - Rear Window Defrost Inop

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Eric Smallwood, Dec 20, 2025 at 9:24 PM.

  1. Eric Smallwood

    Eric Smallwood Junior Member

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    When pushing the button, no light. Not working at all. Any ideas?
     
    #1 Eric Smallwood, Dec 20, 2025 at 9:24 PM
  2. Tideland Prius

    Tideland Prius Moderator of the North
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    Do the mirrors heated up? That way you can tell if it's the switch itself or the rear defroster wires.
     
    #2 Tideland Prius, Dec 21, 2025 at 2:29 AM
  3. Tombukt2

    Tombukt2 Senior Member

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    He wire or lug disconnected so y cause no light I don't believe . Just no heat . Usually in my stuff the adhesive has loosened at one of two lugs on back glass . Atom adhesives is the glue . Course on a gen3 i do not know . 8 have this lug issue right now on two gen2 on site mirrors work back glass no we have MFD no ligh I think on hen2
     
    #3 Tombukt2, Dec 21, 2025 at 7:42 AM
  4. Eric Smallwood

    Eric Smallwood Junior Member

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    Wow, I wish I could understand what you are trying to say. Try using Google translate.
     
    #4 Eric Smallwood, Dec 21, 2025 at 12:05 PM
  5. Tombukt2

    Tombukt2 Senior Member

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    The little Chrome piece came off or is loose not transmitting electricity to make the heat atom cement is the glue . D on can show this used correctly see if trying to undo connectors at rear glass leave you with chrome lug in hand instead of plug.? If so now use the Atom cement to return it to glass plug it up tomorrow
     
    #5 Tombukt2, Dec 21, 2025 at 2:06 PM
  6. Eric Smallwood

    Eric Smallwood Junior Member

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    After I pulled all of the plastic trim off of the rear hatch and verified all connections were sound, I swapped out the control panel from another Prius and it fixed the problem. Apparently, the Rear Window defog switch was shot. This is the 2nd panel I have had to replace. The last one was so dim, you could barely see it.
     
    #6 Eric Smallwood, Dec 22, 2025 at 6:13 PM
    Brian1954 likes this.
  7. ChapmanF

    ChapmanF Senior Member

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    With access to a scan tool supporting active tests, it's also possible to use the scan tool to command the rear defogger on. If that works, and pressing the button doesn't, then you'd immediately suspect the button, or communication from the control panel to the A/C amplifier. Or, if it didn't work that way either, you'd move on to suspecting the amplifier or downstream.
     
    #7 ChapmanF, Dec 22, 2025 at 7:16 PM
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