Hey Scotty hope you’re enjoying Rhode Island, where the air is as salty as rusted frames. I asked on one of your live Q&As about my 2009 GMC Yukon with 130k miles that had a Dimmed Headlight problem. I took your word and I finally went to a mechanic to get it checked out. I was betting on my wallet that it was going to be a ground wire issue. But when I came back to get the statement the mechanic told me that both battery and alternator are working fine, no corrosion or any problems with the ground wire either. He couldn’t tell me exactly what the route of the problem is but he guessed it was the computer that went to the headlight was probably failing. I had to take his word since I also couldn’t think of another explanation for this, what do you think it could it be the computer or something else?
I'm not familiar with that particular vehicle but some things that jump out at me in general...
Is there a headlight relay that might be malfunctioning? In that vehicle the computer might well be triggering the headlights when you turn them on but it would be doing so through some kind of relay, whether electromechanical or solid-state. If it was failing to do so you'd have no headlights at all. (No way is the full current required for the headlights passing through the computer!) Did your mechanic check grounds at the headlight connectors or just at the alternator and battery?
