ACV Heating Circuit Isolation / Diverter Fault

Boiler produces hot water but central heating does not work (combi or system)

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Diverter valve stuck in DHW position, Closed heating isolation valves, Faulty room thermostat or zone valve, Airlock in heating circuit

Safety first: Allow radiators to cool before bleeding.

Check isolation valves: Ensure the flow and return heating valves under the ACV boiler are open.
Check room thermostat and programmer: Confirm they are calling for heat and not set to OFF or low temperature.
Bleed radiators: Remove air from the heating circuit.
Professional diagnosis: A technician should test the diverter valve, zone valves, and control wiring.

Medium 3/5

Diverter Valve Assembly

Check Price on Amazon

We may earn a commission from links on this page.