Vaillant boiler — Vaillant ecoTEC gas boilers covered by the Vaillant United Kingdom fault code list Error Codes Directory
Complete diagnostic reference for Vaillant boiler — Vaillant ecoTEC gas boilers covered by the Vaillant United Kingdom fault code list fault codes. Each code includes official root causes, safety precautions, and affected replacement components.
Vaillant F.23: the temperature spread says water is barely moving
Vaillant defines F.23 as the temperature spread being too great, or water circulation too low. The boiler measures flow and return temperature and compares them, and when the difference grows beyond what the appliance allows, it concludes that not enough water is passing through the heat exchanger to carry the heat away. Applies to: Vaillant ecoTEC gas boilers covered by the Vaillant United Kingdom fault code list The definition used here is Vaillant's own fault code list for ecoTEC appliances sold in the United Kingdom. Vaillant uses different fault numbering on other ranges and in other markets, and a Glow-worm appliance, though part of the same group, has its own published list. Check the code against the label inside your own casing flap. Owner-safe checks: Feel each radiator after a heating attempt and note which get warm, which stay cold, and whether the cold ones are cold at the top or the bottom. | Check the pressure gauge and record the reading, since a system that has lost water often has air in its place. | Confirm that radiator valves and any thermostatic heads have not been closed off, particularly on circuits recently worked on. Qualified technician: Setting or replacing a pump, venting a sealed primary circuit, power flushing, and testing flow and return sensors are Gas Safe registered tasks on this appliance. | Kettling or banging from the boiler is a reason to stop using the heating rather than to keep trying, because boiling against the exchanger causes cumulative damage.
Vaillant F.32: no fan means no combustion, by design
Vaillant gives F.32 as the fan being faulty or not connected. On a room-sealed condensing boiler the fan is what draws combustion air in and pushes flue gases out, so the appliance cannot burn gas safely without it. The lockout is not the boiler being cautious; it is the only acceptable response to losing forced draught. Applies to: Vaillant ecoTEC gas boilers covered by the Vaillant United Kingdom fault code list This definition comes from Vaillant's fault code list for ecoTEC appliances in the United Kingdom. The same number means something else on other manufacturers and on some Vaillant ranges outside the ecoTEC family, so read it against the list printed inside the casing flap of your own boiler. Owner-safe checks: Listen at the start of an attempt and note whether any fan sound occurs at all, and whether it sounds as it used to. | Record the exact code and how many attempts produce the same result before you stop trying. | Check whether any recent service, part replacement, or electrical work preceded the fault. Qualified technician: Testing, cleaning, or replacing a boiler fan and its wiring is Gas Safe registered work on a sealed combustion appliance in the United Kingdom. | Resist the urge to take the front panel off for a look. On a room-sealed appliance that panel is a safety component, and opening it breaks the separation it exists to maintain.