Adding phone charger to unused heated seats wiring

Discussion in 'Gen 3 Prius Accessories and Modifications' started by Dorin Giurgiuca, Mar 24, 2024.

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  1. Dorin Giurgiuca

    Dorin Giurgiuca Junior Member

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    Hey everyone!
    I did something today.. i read on a different thread that behind the blank button for heated rear seats fo xw30, there is the switch wiring and it has 12v @ ACC. i ordered a usb charger with voltmeter from and chose the highest wattage (45w).
    Screenshot 2024-03-24 205543.png

    Fast forward to today, i removed the plate and found the plug and the +12v and ground wires. Soldered the chager and it all works great. The problem is i now have wire gauge anxiety because the wires for the button are really thin (like 10 strands of copper) and i'm not confident they can take 45w. My question is, is it safe to assume that because the fuses for the heated seats are rated at 10A, the system should support up to 120w? Or is the fuse just for the heating elements? What would the rating be on the wires going to the button?
    Here's a picture of the plug & wires: 20240324_154656.jpg

    Thanks!
     
    #1 Dorin Giurgiuca, Mar 24, 2024
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  2. ChapmanF

    ChapmanF Senior Member

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    45 watts means less than 4 amps, so I would not be concerned about ampacity, as long as you looked in the wiring diagram and identified the right wires to use.

    Toyota Service Information and Where To Find It | PriusChat

    Modern automotive wiring is skinnier for the same ampacity than you would be accustomed to from home wiring, because it uses thinner insulation with a much higher temperature rating, which then can handle the heat from thinner-gauge copper, and all of that saves weight.

    The other consideration is whether you should leave the circuit fused at 10 amps. As your accessory is only rated for a little under 4, a good idea would be to remove the 10 amp fuse and use one closer to the maximum the accessory is designed for. Otherwise, a fault in the accessory could draw current that would not blow the fuse or damage the Toyota wiring, but could be incendiary within the accessory itself.
     
    #2 ChapmanF, Mar 24, 2024
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  3. Dorin Giurgiuca

    Dorin Giurgiuca Junior Member

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    I've considered switching to a 5A fuse and will do that as soon as i can find one.
    Regarding the schematics, i have only checked the presence of +12v and GND, but now that you mention it i will look at the diagrams to be safe.

    Thanks!
     
    #3 Dorin Giurgiuca, Mar 25, 2024
  4. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I don't think they ever used a seat heater rated as little as 45W- so I think you're set.

    Neat find, thanks for sharing!
     
    #4 Leadfoot J. McCoalroller, Mar 25, 2024
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  5. Dorin Giurgiuca

    Dorin Giurgiuca Junior Member

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    Here are some pics of the final product, in case anyone is interested. I also replaced the blank below the start/stop button with a USB+AuxIn connected to the android HU.
    20240325_083215.jpg 20240325_083220.jpg 20240325_181952.jpg
     
    #5 Dorin Giurgiuca, Mar 25, 2024
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