You may have a relay that is failed, the light switch has failed or is grounding out making the circuit complete even without switch on, a short in the, "ON" position circuit of the igniton switch or a bad control unit if you have Auto lamps.
In this post and the next are the wiring diagrams for the exterior light circuits.
Start with the headlight switch in the "OFF" position and see if it is putting out 12 V right out of the terminals of the switch. If it is, it probably is the switch that is bad.
Check in the same manner for each relay.
If you need anything else come back to us anytime.
Wednesday, October 5th, 2011 AT 8:52 PM