Gledhill water heater shows E03 and does not call for heat from boiler or immersion

Safety: Switch off the electrical supply and allow the store to cool. Do not remove the front cover until power is isolated.

Steps:

• Find the cylinder thermistor: On Gledhill thermal stores (e.g. Boilermate, Systemate, Gulfstream), the main store thermistor is usually inserted into a dry pocket on the front or side of the cylinder body, often mid‑height.
• Check seating: Ensure the sensor is fully inserted into the pocket and secured with its clip or retaining spring. A loose sensor can cause incorrect readings and E03.
• Inspect cable: Follow the cable back to the PCB. Look for chafing where it passes through grommets or behind panels. Repair or replace damaged cable.
• Test resistance: Disconnect from PCB and measure resistance. Compare with Gledhill’s NTC chart. If open‑circuit or shorted, replace the thermistor.
• PCB evaluation: If the thermistor tests correctly and is properly seated, but E03 persists, the PCB input may be faulty. Check for signs of overheating or moisture damage. PCB replacement is usually required.

After replacement: Clear the error by power‑cycling the unit and confirm that the store heats and maintains temperature correctly.