86 F-150, Engine Dies When Turn Headlights On

[VehicleNut]

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?

[mustangmike351c]

check you grounds at the engine and the body.

[VehicleNut]

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?

[mustangmike351c]

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

[VehicleNut]

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.