What dry means
There's not enough water in the heater to start it. The spa stays shut down until the problem is fixed and you press a button.
Also shown as: M027, Heater dry, depending on the model.
Likely causes
- Low water
- Airlock
- Severe flow restriction
Safe first checks
- Fix the water level and airlock, then press any button to reset.
When to stop
If it repeats, call for service.
Checked against: Balboa TP500S / TP600 system user guide (42339 rev A1): message codes. Codes can differ by model and year, so confirm with your owner's manual.