I have an 86 740 wagon that runs great except for one electrical problem: lights, wipers, radio,and horn do not function unless I switch on the headlights before starting the car. All components then function normally, and none of them in my 1000 miles of ownership has ever shut down while the car is running. When I got the car last week, there was another peculiarity at first: the bulb failure light came on only when the lights worked! Now, the bulb failure light comes on only when the parking lights are on. I’ve checked all the bulbs--each works. It’s as if a switch is turning off everything at once and only starting the car up with the lights on corrects the problem. Could this all be attributable to a faulty bulb relay? Ignition switch problem?
I appreciate the help.

PVC