Vaillant CI-SI Boiler Error Codes

Fault Codes Fault Description Possible Causes
Fault Code F1 Ignition Failure Insufficient Inlet Working Gas Pressure At The Appliance
Flue Problem
Spark Generation Issue
Incorrect Gas Valve Adjustment (Minimum Burner Pressure Set Too Low)
Flame Rectification Issue
Combustion Issue (Poor Flame Picture)
Software Error On The Main PCB Or The User Interface PCB
Fault Code F2 Air Fault Fan Fault
Fan Venturi Blocked
PCB Fault (No Power To The Fan)
Wiring Harness Fault Between The Fan And The Main PCB
The Air Pressure Switch Is Not Switching To The N/O Position When The Fan Is Running
The Air Pressure Switch Jammed In The “Made” Position Prior To The Fan Operation
Fault Code F3 Air Fault Fan Fault
Fan Venturi Blocked
PCB Fault (No Power To The Fan)
Wiring Harness Fault Between The Fan And The Main PCB
The Air Pressure Switch Is Not Switching To The N/O Position When The Fan Is Running
The Air Pressure Switch Jammed In The “Made” Position Prior To The Fan Operation
Fault Code F4 Flame Sensing Fault Insufficient Inlet Working Gas Pressure At The Appliance
Flue Problem
Incorrect Gas Valve Adjustment (Minimum Burner Pressure Set Too Low)
Poor Combustion (Poor Flame Picture)
Flame Sensing Electrode Faulty Or Incorrectly Positioned
Incoming Power Supply Issue (Reverse Polarity, Neutral Fault, Earth Fault)
Software Error On The Main PCB Or The User Interface PCB
Fault Code F5 Overheat Fault The Overheat Thermostat Has Activated In The Appliance Due To Poor Circulation (115C)
Pump Not Running
Appliance Heating Return Filter Blocked
Air Lock Within The Boiler Or The System
Blockage Within The Boiler Or The System
System Design Issue
Insufficient System Bypass
NTC Thermistor Out Of Calibration (Should Read 12Kohms @ 20C)
Harness Fault Between The Overheat Thermostat And The Main PCB
Fault Code F6 Thermistor Fault The NTC Thermistor Has Gone Open Circuit (Should Read 12Kohms @ 20C)
Wiring Harness Fault Or Connection Fault Between Thermistor And The Main PCB

Leave a Comment

Scroll to Top