turn on headlights & engine stumbles?

[blackmag17]

I posted a thread a few weeks ago where I installed a new battery and then there was no power to the car; battery was good but nothing on the car worked. So I installed the battery again today to show a friend how nothing worked. Turned the key to the Run position and no lights in the instrument cluster or interior came on. I then turned on the headlights and immediately they came on, as well as all the lights in the instrument cluster and interior. I turn the key to the Start position and the car starts.

I turn off the headlights and let the car run awhile. I then turn on the headlights, the engine stumbles (as if it were going to die) and all the lights fade for about 2 seconds. Then the car goes back to normal idle and the lights back to normal. Now the car is fine.

Anyone have any ideas what could cause this?

 

[crewchiefpro]

Sounds like a wiring harness problem. When nothing makes sense then it is time to go through the harness to see if the coverings are coming apart.

 

[Beans]

Sounds like a ground isn't hooked up correctly.