Furnace shows F37, low system pressure warning, heating may be intermittent

Safety first: Allow the system to cool before topping up. Do not exceed the maximum pressure indicated on the gauge.

• Top up pressure: Use the filling loop to raise pressure to the recommended cold value (usually 1.0–1.5 bar). Close the filling valves securely afterwards.
• Bleed radiators: Remove trapped air from radiators and recheck pressure.
• Check for leaks: Inspect radiators, valves, and visible pipework for signs of water. Persistent pressure loss requires leak repair.
• Sensor check: If pressure is correct but F37 persists, the pressure sensor or gauge may be faulty and should be replaced.