Showing results for 
Search instead for 
Did you mean: 
Hagerty Employee

Piston Slap: That ballast diagnosis flex?

B writes:

I have a 2013 Flex with HID headlights. One side goes out after 20 minutes of driving, and looking online I see that it has a ballast for each of the headlights. The headlight also comes back on when I turn the lights off and back on again.


Question is: Do I replace the bulb or the ballast? The bulb can be reached under the hood but the ballast requires the bumper to be removed.


Sajeev answers:

Bulbs are usually not picky on when they want to illuminate: Either they light up (to some degree) or they burn out. Again, usually. Even worse, HID ballasts often possess the same symptoms. So what’s the best way to get to the bottom of this?


Read the full article on