Headlight thunk

[Diesel Nut]

When driving or idling, if the headlights haven't been on for a while, like overnught, or driving all day and it gets dark, there is a noise under the hood comperable to the AC compressor noise when you turn the lights on. Doesn't do it with parking lights, but as soon as you turn that knob one mo detent, THUNK! It did it driving a few days ago and it felt like it briefly bogged the engine down pretty good, like hitting a big pothole without all the bouncing. Anyone els with this problem or ideas? Just started doing this about 2 months ago. Help!

 

[rbattelle]

Wow, that is weird wild stuff. Is there any indication of a change in the voltmeter? The only thing I can think of is there's a massive short somewhere that's pulling huge amperage on the system when you first turn on the headlamps. You'd think that would blow the fuse though.

 

[Diesel Nut]

no change in voltmeter, and no other electrical problems to date. Still haven't blown any fuses yet. Beats me!

 

[Patriot_RAM]

Mine makes the same noise. I have a Brite Box installed. I wonder if that makes any difference.