What happened
During a climb from flight level 330 to flight level 370, the first officer observed sparks and smoke emanating from the left side panel beneath his glare shield. In response to the developing situation, the cockpit lights were turned off, which caused the smoke to cease. The flight crew returned to Minneapolis and landed without incident.
The investigation
An inspection of the aircraft disclosed that the fire originated in a wire bundle located between the center of the instrument panel and the fluorescent light underneath the first officer's glare shield. The wire bundle had been reinstalled four days prior to the event. It was stretched tightly across the left end of the fluorescent light and forced to turn an abrupt angle across a sharp metal edge on the light fixture.
The insulation and fabric sleeve surrounding the wires were burned, leaving the conductors exposed. Testing of the circuit breakers did not determine why they failed to open during the incident.