I have a 2013 FX4 with factory HID lamps. The left headlamp comes on when the truck is turned off. I have checked and there is power to both sides when truck and switch if off. The left lamp will turn it self on for no apparent reason. Could it possibly be a bad Ballast. Hopefully someone has run into this problem before.

 

3 things could cause that,

1) Someone monkeying with the wiring installing other electrical things.
2) Body Control Module.
3) Ballast.

Check for non oem wiring near the affected light. as well as in the passenger kick panel where the bcm is located. Swap sides with the ballast and see if the issue follows it, if the left light still does it then your bcm is likely the cause.

P.S. If after swapping ballasts you no longer have any issue, it was likely a faulty connection at the ballast connector

 

Thanks... I am going to swap the ballast to see if the left side has the same issue. Haven't considered the BCM but I will now.