High beam always works on with headlights - can’t turn it off!

[bug616]

Side lights work normally. High beam flash works normally. When I put low beam on, high beam comes on as well with the blue light on the dash. Moving high beam selector on and off makes no difference.

I’ve checked relays and they’re all good - swapped them out with another truck to be sure. Checked all fuses. Had the light switch apart and it’s all good. Tried disconnecting each high and low beam in sequence and I makes no difference.

I’m stumped! If I understand correctly it may be a bad earth. Will look at electrical FSM but would welcome any ideas…. Is there anything obvious I should check?

 

[bug616]

Solved! Part of a HID harness had gone bad on one side. I had disconnected the HID but left the harness in place previously.

 

[TomRodz]

Hey, what is the HID harness and where does it disconnect? I have the same issue.

 

[bug616]

HID is retrofit not OEM. Unless you or the PO fitted, you won’t have it.

 

[western flyer]

Hey, what is the HID harness and where does it disconnect? I have the same issue.

HID, or high-intensity discharge light bulbs and lamps, are a family of gas-discharge arc lamps. As bug616 noted, you likely do not have such a wiring harness for HID headlights (unless installed by you or PO) as it would be aftermarket for retrofit bulbs and not OEM. TomRodz, I suggest you download the EWD manual (electrical wiring diagram, linked below) to see the various ways the low beams and high beams can get power. That should give you some strong hints as to where your high beams are getting power even when they should not be. Think grounds... Cheers.

Electrical Wire Diagram

Was installing the PITA ARB rear bumper and needed to figure out the tail light issue with their wiring. Found this online. Thought it may be useful.? It's a lot, but sure did answer my questions and I'm sure I will need it again. Well...How do I post a PDF??

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