Gledhill water heater displays E03 and does not call for heat from the boiler or immersion.

Safety: Switch off the electrical supply and allow the store to cool. Do not remove the front cover until the power supply 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 at 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 an E03 error.
• Inspect cable: Follow the cable back to the PCB. Look for chafing where it passes through grommets or behind panels. Repair or replace any damaged cable.
• Test resistance: Disconnect from the PCB and measure its 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 the E03 error 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 the temperature correctly.