No headlights with ignition in run position
 

OK, have lights when key is off. when engine is started (key in run) no headlights. all other lights work. this is a 93 half ton 4x4. it has a plow but it isn't on truck now. ever hear of this in a GM or is it in plowing wiring? Thanks in advance.

I've seen some weird stuff with an aftermarket plow unit before ... My first suspition would be the plow module. If a plow dealer installed the plow and module on there, I'd take it back and have them look it over.

For the record, I wasn't able to figure out what was wrong with the truck and plow that I mentioned.

fixed it... switch on plow unit from truck to plow went bad. If I would have had the plow on it, I would have had head lights. working fine now...