**Tankless Water Heater Service – Navien NPE-240A** **Work Performed:** - Responded to service call for Navien NPE-240A tankless water heater displaying error code **E538-00 (Abnormal RTC – Check Panel PCB)**. - Verified all wiring harnesses and connectors between the front panel PCB and main control board — all connections secure. -issue happening internally control board PCB - Checked all operating parameters. - Performed system reset and reinitialized all parameters for proper operation. - Restored functionality and confirmed the error code cleared successfully. **Results:** - System operating normally after reset. - Cycled hot water multiple times and monitored performance — no error codes reappeared. - Client had continuous hot water during testing. **Recommendations:** - Client is under parts warranty until 2029. - If error code **E538-00** returns, replacement of the front panel PCB may be required under warranty. - Continue to monitor system operation and conta