As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE MAINTENANCE TEAM REPORTED THAT THE APU FIRE WARNING DISCHARGE BUTTON WILL NOT ILLUMINATE DURING LAMP TEST TROUBLESHOOTING DETERMINED THAT THE PUSH BUTTON SWITCH P/N 13740-002 WAS DEFECTIVE. THE SWITCH WAS REPLACED WITH NEW. OPS CHECKS WERE SATISFACTORY.