The Micro Tech II MQ‑LDT1100‑0 (part 060006301) is a keypad controller used in industrial HVAC and energy‑management systems to provide user interface and local monitoring of process parameters. Common failure points for this class of controllers include burnt or tripped power‑distribution circuits, degraded LCD backlight LEDs, and failed communication modules (e.g., RS‑232/RS‑485). Initial troubleshooting should verify the 24 V DC supply voltage and continuity to the keypad, inspect the LCD panel for flickering or dead pixels, and review any stored error codes via the controller’s diagnostic port. If power and visual inspection are normal, test the communication lines with a loopback tester and check the firmware integrity by re‑flashing if necessary.[oss-gpt-20b]