Boiler displays E11, pressure gauge appears normal but boiler will not run

Safety first: Isolate power before removing covers.

• Confirm actual pressure: Check the mechanical pressure gauge on the ACV boiler. If it shows normal pressure but E11 is present, the electronic sensor may be faulty.
• Power cycle: Turn the boiler off and on at the isolator to clear transient faults.
• Visual inspection: A competent person can check that the pressure sensor (usually mounted on the hydraulic block) is firmly connected and that its capillary or tapping is not visibly leaking.
• Professional diagnosis: A technician should remove and inspect the sensor connection for blockage, test the sensor output, and replace it if necessary.