Grant Vortex Pro Combi 26 Fault codes & diagnostics

10 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

CombiOil Oil 26 kW 2013-present

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Severity at a glance

Each cell = one fault code. Hover to identify.

10 High

Fault codes

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Locate the external filling loop, which is a flexible silver hose connected to two valves under the boiler.
Slowly open both valves to allow mains water into the system until the pressure gauge reads between 1.0 and 1.5 bar.
Close both valves tightly and ensure the boiler resets itself.

Locate the external filling loop, usually found underneath the boiler.
Open the small valve(s) to allow mains water into the system while watching the pressure gauge.
Stop filling once the needle reaches the green zone, typically between 1.0 and 1.5 bar.
Ensure the valve is fully closed tightly to prevent over-pressurisation.

Check that your room thermostat is turned up higher than the current room temperature.
Ensure your programmer or timer is set to 'ON' or 'AUTO'.
Check if the batteries in your wireless thermostat need replacing.

Check that the boiler's main power switch is turned to the 'ON' position.
Inspect your home's main consumer unit (fuse box) to see if a circuit breaker has tripped.
Check the fused spur switch (usually near the boiler) and replace the 3-amp fuse if it has blown.