As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PRIOR TO TAKE OFF, DURING THE FLOAT SYSTEM TEST, WHEN THE TEST SWITCH WAS PLACED IN THE TEST POSITION ALL CAUTION LIGHTS ILLUMINATED. (SAME AS PRESSING CAUTION PANEL TEST SWITCH). THE PILOT ALERTED MAINTENANCE, THE MECHANIC REMOVED AND REPLACED THE CAUTION PANEL AND THE AIRCRAFT WAS RETURNED TO SERVICE.