I have a 2001 sebring convertable 2.7 V6, when I have the headlights on my heater is blowing cold air, turn them off and hot air blows, the dash lights at the temp knob and the fan speed knob are also off.occured at the same time.

I would expect this is more to do with a low coolant level than an electrical issue. If your coolant is low when you turn off the headlights your engine revs will increase slightly increasing the pressure in your coolant system and pushing fluid into your heater core.
Check your coolant reservior when your car is cold (first thing in the morning), it should be at max cold. If it is lower than this you may not have warm coolant in your heater core.
If this is the case...then where did your coolant go?
Most likely the thermostat/temp housing is leaking...replaced both on my two 2001 sebrings...common issue..~$150 for parts and a little awkward to install but fairly easy fix.