As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MSP - FLT NR 421 - AFTER TAKEOFF, THE LEFT OIL PRESSURE WARNING LIGHT ILLUMINATED WITH ALL OTHER INDICATIONS NORMAL. THE AIRCRAFT RETURNED TO MSP FOR MAINTENANCE TO INSPECT. INSPECTION OF THE SYSTEM FOUND THE OIL PRESSURE WARNING LIGHT SWITCH STUCK CLOSED. THE SWITCH WAS REPLACED AND ALL INDICATION WERE NORMAL. THE AIRCRAFT WAS RELEASED. (M)