Safety first: Turn off power at the GFCI breaker before working on the spa.

1. Correct water and flow issues first: Follow the steps for dr/FLO errors: verify water level, clean filter, bleed air from heater and pump, and confirm circulation.
2. Allow heater to cool: Leave power off for at least 30 minutes to let the heater and sensors cool down.
3. Reset system: Restore power and see if the dy code clears. If it returns immediately, the control system may be detecting a sensor fault.
4. Inspect temperature sensors: Locate the heater temperature and high-limit sensors (usually threaded into the heater tube). Check for loose connections, corrosion, or damaged wires.
5. Do not bypass safety devices: Never jumper or bypass sensors to clear the error; this is dangerous and can cause heater damage or fire.

If dy persists after resolving flow issues, the heater sensors or control board may need replacement. This is typically a technician-level repair.

Control panel shows dy or DY and heating is disabled.

Possible Causes