Have Mustang 2016. Had to replace my 35w HID for 25w (legal reasons) and now headlight wont turn off until I disconnect battery or pull fuses. All parts are made by Osram and Plug'n'Play. Normally you would say "Check relay" or "Check fuses" and this is where it gets bizarre- I switch 35w parts back on and everything works fine. Connected car to Forscan, no fault codes. What can be different that 25w parts don't like, but for 35w parts it is fine. Logically there can't be.

  • How do you turn these on and off? Just the usual headlight switch?
    – GdD
    Oct 19, 2021 at 16:10
  • What is meant to be on the car?
    – HandyHowie
    Oct 19, 2021 at 16:47
  • Normally, yes. I turn headlight knob to 0. Obviously at that position drl are automatically on as long as you have auxiliary power on. But right now...auxiliary power is off and those aren't even drl light (those are low beam), and the light are still on. Oct 19, 2021 at 16:47
  • @HandyHowieBoth 35w and 25w are used on Mustangs. US version uses 35w and EU uses 25w. In EU some countries require washers and levelers on 35w lights. So for EU version Ford has installed25w lights on Mustangs so that they wouldn't have to install levelers and washers. Mine is originally US spec, that came with 35w and because of no washers and levelers I am required to downgrade those 35w to 25w. Oct 19, 2021 at 16:52
  • So you have replaced the ballasts and bulbs/lamps?
    – HandyHowie
    Oct 19, 2021 at 17:11


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