Headlight Problem Options

[yeahmag]

I have a very strange problem. My headlights work fine until I start the motor. Specifically, with the ignition all the way on, but the engine off, the headlights work as expected. With the engine running they will not come on at all. If the headlights are on and I start the motor they turn off, but stay in the upright position.

Ideas?

[yeahmag]

If the problem was with the switch I think I'd see other systems failing. Is there a relay that turns off the sub systems when cranking? The only thing that's not functional after starting is the headlights.

[jcd914]

If the problem was with the switch I think I'd see other systems failing. Is there a relay that turns off the sub systems when cranking? The only thing that's not functional after starting is the headlights.

There is no relay to turn off the accessory load, it all goes thru the ignition switch.
Pelican has the wiring diagrams in their site and you can trace out the accessory power from the switch to a couple different fuses. There should be something other than the head lights that are affected if the switch is failing but I would still check it first, since it is a common failure. The wiring to or from the fuses may not be connecting correctly. Since all the connectors at the fuse panel are standard spade connectors it is easy to put connectors on the wrong fuse connector.

Use the diagram to find the accessory wire fro the ignition switch and hook a voltmeter or test light and start the car, does it keep it's power?

I worked with a tech that constantly drilled me with "Test, don't guess" and "Work smarter, not harder", good advise (a bit annoying but good).

Good luck.
Jim