Verified boiler fault code
Vokèra A04 Fault Code (Vision C)
Insufficient system water pressure.
Safety disclaimer
Fault code summary
- Manufacturer
- Vokèra
- Fault code
- A04
- Fault type
- Low pressure, Pressure sensor
- Severity
- lockout
- Reset
- The Vision C table says check/refill system pressure, reset and check appliance operation.
- Applicable models
- Vision Combi 25 C, Vision Combi 30 C
Quick answer
Insufficient system water pressure.
What does this fault code mean?
Insufficient system water pressure.
Common causes
- System water pressure is insufficient.
Symptoms
- Vision C displays A04 as a final alarm.
What can the homeowner safely check?
- Read the system pressure gauge; do not remove the boiler casing.
Boiler reset information
The Vision C table says check/refill system pressure, reset and check appliance operation.
When should I call an engineer?
Contact a suitably qualified heating engineer when the fault persists, the boiler locks out, or the manufacturer instructions do not resolve it. For gas appliance work in the UK, use a Gas Safe registered engineer.
Engineer diagnosis
- Check pressure, possible water loss and pressure sensing.
Applicable boiler models
Related fault codes
- A01 — Vision C
Ignition failure, flame not sensed, or internal fault.
Read fault code - A02 — Vision C
Limit thermostat fault.
Read fault code - A03 — Vision C
Fan tachometer signal fault.
Read fault code - A06 — Vision C
Domestic-hot-water thermistor fault.
Read fault code - A07 — Vision C
Primary-flow thermistor fault, overtemperature or temperature differential condition.
Read fault code - A08 — Vision C
Return thermistor fault, overtemperature or inverted temperature differential.
Read fault code - A09 — Vision C
Flue thermistor or flue-thermistor counter fault, or flue thermistor overtemperature.
Read fault code - A77 — Vision C
Low-temperature thermostat fault.
Read fault code
Manufacturer documentation
Vision C Users Instructions, Installation & Servicing InstructionsFAULT CODES — A04: Insufficient system water pressure; Final; Check/refill system pressure, reset, check appliance operation.
Last verified
2026-09-12
Frequently asked questions
What does Vokèra A04 mean?
Insufficient system water pressure.
Can I reset a Vokèra A04 fault?
The Vision C table says check/refill system pressure, reset and check appliance operation.