Micro Tech II MQLDT1100-0 Controller

The Micro Tech II MQLDT1100‑0 is a keypad controller used in McQuay/Johnson HVAC chiller and rooftop unit systems, providing user input and local control of the associated PLC. Common failures on this board include power supply degradation (brown‑out or intermittent operation), keypad button failure or stuck contacts, and LonWorks communication module faults that cause loss of remote command reception. First‑check steps are: verify 24 V DC input voltage and continuity to the controller; inspect the keypad for physical damage or debris and test each key with a multimeter; review any stored error codes on the display or via the serial/LonWorks interface for communication errors.[oss-gpt-20b] Post Comment

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