I have a 98 blazer thats having some issues.if i turn my head lamp switch on with key off it powers on fuel pump.ignition and half my dash cluster.the head lamps them selves arnt powering on.no power being sent to head lamp plug at bulb.if i turn the head lamp switch on with the rig running it kills the rig.i have checked and cleaned every ground and positive conection.ive replaced every relay under the hood including the ones under the dash on the drivers side.i chacked power and pins for all relays and everything correct.from what ive read the bcm could of gone bad.has anyone has similar problems

 

I'd be more inclined to think that you have an ignition switch problem. Common in these trucks.