86 F-150, Engine Dies When Turn Headlights On

I have an 86' 302, fuel-injection. I can start the truck fine, no problem. It starts like you would expect, hold the key in for a few seconds.

However, while in idle and I turn headlights on, the truck dies completely, no power. No power what so ever, just dead. When I push the headlight switch to just parking lights, the dash lights and key buzzer come on like it is ready to start. I can start again, right away, no problem. I pull the headlight switch all the way out again, bam!, dead as a door nail. I can repeat this process again and again.

I have checked the battery and even changed the alternator, thinking it may be a bad voltage regulator.

I can't figure it out. Can anyone help?

check you grounds at the engine and the body.

Checked both the engine and body ground with an ohmeter. Both are good. Changed headlight switch and dimmer switch. Still the same problem.

Any other suggestions?

check the power wires on the starter sol. clean them with a wire brush. the head lights must be get their power from one of the other wires instead of the battery killing the power to everything else. let me know

Found a bad electrical connector (gray) next to the starter solenoid towards the engine. It is behind the black vacuum transducer housing & has about 4 wires in it. The green wire was corroded thru. Took connector off and spliced & heat shrunk wires. No problems now. I would suggest all that own this year or close model to check these type connectors. I counted about 4-6 under the hood. Some are black connectors.

Thanks for the tips.