A.O. Smith BTX-100/GDHE-50 – UIM

The UIM (User Interface Module) is the display on the front of the water heater. The UIM’s major components include a Circuit Board with LCD display and a Button Pad Overlay which contains the five user input buttons.

Service Notes – Button Pad Ribbon Cable
The Ribbon Cable that connects the Button Pad Overlay to the UIM Circuit Board must be plugged in exactly as shown in the images below; with the metal crimp connections visible on the plug end and the UIM Circuit Board back facing out. There are six pins on this Ribbon cable socket, Ensure all six pins are inserted into the Ribbon Cable plug whenever removing or installing the UIM or Button Pad Overlay.

Failure to connect this Ribbon cable exactly as shown when servicing will render the User Input Buttons inoperable. This should be checked whenever the nature of the service complaint is an inoperable or unresponsive controller or UIM.

User input buttons on the UIM include an Up, a Down, and three Operational buttons.

The Up and Down buttons are used to navigate through the various menus and screens displayed and to adjust or change user settings such as the Operating Set Point.

The three Operational buttons are multifunctional. Their function is defined by the text that appears above each button on the UIM display. The Operational button’s function will change depending on what menu or screen is currently displayed.

Commercial & Residential Product Differences

The illustration below shows the control system’s “Desktop” screen. This is the control system’s default screen. If there are no active fault messages and no user input for approximately 10 minutes the control system will return to this screen automatically.

The water heater covered by this Service Manual is available in commercial and residential models. The “Tank Temperature” data shown on the desktop screen below will not be visible on residential models. Tank Temperature will be displayed on the commercial models only.

The maximum Operating Set Point for a residential model will be 160°F (71°C). Maximum Operating Set Point on commercial models will be 180°F (82°C).

Discreet Menu – Contact Information
While viewing the Desktop screen (above). Press and hold down the middle Operational button for 30 seconds and then release it. This will launch a discreet menu with a provision for entering personalized contact information. Installing contractors and/or service technicians can enter their company name and telephone number. This contact information would be displayed with all fault messages whenever the control system was in a lock out condition.