Machine powers on but does not heat, temperature display (if equipped) shows error or remains at room temperature, no boiler warm-up.

Safety first: Unplug the machine and allow it to cool completely before removing covers. Heating components can remain hot for a long time.

• Listen for heating activity: When first powered on, you should normally hear a slight click from the relay and see the pressure gauge slowly rise. If there is no click and no pressure increase, suspect the heating circuit.
• Check high-limit thermostat: Many Rocket boilers have a manual-reset safety thermostat on top of the boiler. Remove the top cover and look for a small round device with a red or black reset button. Press firmly to reset. If it clicks, power the machine back on and test.
• Inspect element wiring: With the machine unplugged, check the spade connectors on the boiler heating element. Tighten or reseat any loose connectors and look for burned insulation.
• Measure element resistance (advanced): Using a multimeter set to ohms, measure across the heating element terminals. A reading of open circuit (infinite resistance) indicates a failed element that must be replaced.
• If the element tests good: The fault may be in the SSR/triac or Gicar control box. These are live-voltage components; replacement is best handled by a professional technician.