Gas Safe: Gas work, flue work, and PCB replacement on a gas boiler must be carried out by a Gas Safe registered engineer. Homeowners can check obvious items such as heating pressure, condensate overflow, and whether a control is unplugged — then call an engineer.
Always confirm the part number against the boiler GC number and the installation manual before ordering.
Overview
F.02 is an actoSTOR cylinder-charging NTC open circuit. Vaillant only expects this with F.91 (actoSTOR electronics). It is not a standard ecoTEC combi flow/return NTC fault.
Vaillant meaning: Interruption cylinder charging sensor actoSTOR (NTC) — only in combination with F.91
Possible causes
- Charging NTC defective or unplugged
- NTC cable damaged
- Poor plug on the NTC or on the actoSTOR electronics
- actoSTOR module itself not communicating (F.91)
Possible solutions
- Confirm the appliance actually has actoSTOR / a Vaillant store. If not, you are on the wrong fault tree.
- Check F.91 is also present. Diagnose actoSTOR electronics and interconnect first if it is.
- Inspect the charging NTC plug and measure the sensor.
- Refit or replace the NTC lead, then the charging NTC, then the actoSTOR board if the sensor circuit is sound.
Possible parts needed
- actoSTOR cylinder charging NTC (confirm from the actoSTOR / store spare-parts list and GC number)
- NTC cable / harness
- actoSTOR electronics module