Control panel displays Sn2 and spa may not heat or may shut down

Safety first: Shut off power at the GFCI breaker before touching any components. Do not work in standing water.

Steps to troubleshoot Sn2:

• Reset power: Turn the breaker OFF for a few minutes, then ON. If Sn2 reappears, proceed.
• Locate the high-limit/secondary sensor: Open the equipment bay and find the second sensor on the heater manifold or in a separate sensor well, usually labeled HI-LIMIT, SENSOR B, or similar on the control board.
• Inspect the connector: Unplug and replug the sensor connector on the control board. Look for green corrosion, moisture, or bent pins. Dry any moisture with a clean cloth and allow the area to air dry.
• Check cable and probe: Follow the cable from the board to the probe. Look for cuts, melted insulation, or kinks. Inspect the probe body for cracks or discoloration from overheating.
• Replace the sensor: With power OFF, remove the old high-limit/secondary sensor from the heater manifold or well. Install a Strong Spas-compatible replacement sensor with a new O-ring. Tighten only enough to seal; do not overtighten plastic threads.
• Test operation: Restore power and monitor the display. If Sn2 clears and the spa heats normally, the repair is complete.

When to call a technician: If Sn2 persists with a new sensor, the control board’s sensor input may be damaged, requiring professional testing or control pack replacement.