Controller is stuck showing 'tSt' or 'TEST' and does not operate solar heating normally.

Safety: Use caution when pressing buttons on a live controller; do not open the enclosure while power is on.

• Exit test mode: Press and hold the MODE or EXIT button (as per the manual) for several seconds to exit test mode.
• Power-cycle: Turn off power for 30 seconds, then restore it without pressing any buttons. If 'tSt' appears immediately, a switch or DIP setting may be stuck.
• Inspect dip switches: With power off, open the controller and locate any configuration DIP switches. Ensure the 'TEST' or 'INSTALLER' positions are set to 'NORMAL'.
• Check keypad: Look for stuck or damaged buttons on the front panel. If a button is physically jammed, gently free it. If the keypad is defective, the front panel or the entire controller may need replacement.