What was found
IN THE DESCENT PORTION OF THIS FLIGHT, THE FIRE T HANDLES, BOTH FIRE EXTINGUISHER ARMED LIGHTS, BOTH MASTER CAUTION WARNING LIGHTS, SECONDARY INVERTER LIGHT, AND A SPARE WARNING LIGHT ALL ILLUMINATED AT THE SAME TIME. CREW OBSERVED NORMAL ENGINE INDICATIONS (ITT, OIL TEMP, ETC), FOLLOWED THE CHECKLIST FOR THE SECONDARY INVERTER (WHICH DIDN'T CHANGE THE SITUATION), AND CAME TO THE CONCUSION THAT THESE WERE ERRONEOUS INDICATIONS. CREW LANDED SAFELY. MX TROUBLESHOT THE ISSUE AND DETERMINED THAT THE MASTER WARNING CONTROL UNIT HAD FAILED. MX REPLACED THE MASTER WARNING CONTROL UNIT WHICH CLEARED THE DISCREPANCY. NO FURTHER ISSUES WITH THE INDICATION SYSTEM HAVE BEEN NOTED.