Viessmann Boiler Error Codes
Complete guide to Viessmann boiler error codes with safety information and troubleshooting steps.
Important Safety Notice
Viessmann boilers use alphanumeric codes. "F" codes indicate faults requiring attention. "A" codes are operational alerts.
Never bypass safety devices or ignore repeated lockouts.
Call Now: 778-909-5731Safety Level Key
SafeSystem protected, low risk
CautionMonitor and call technician
DangerCall technician immediately
Common Viessmann Error Codes
Error Code F2
Sensor Short Circuit
What You Can Check
- •Note which sensor (displayed on screen)
- •Check for loose wiring
Error Code F4
Sensor Open Circuit / Break
What You Can Check
- •Check sensor connections
- •Note temperature readings
Error Code F5
External Safety Device Triggered
What You Can Check
- •Do not reset repeatedly
- •Check for visible issues
Error Code F6
Internal Safety Device Triggered
What You Can Check
- •Turn off unit
- •Check for overheating
Error Code A1
Burner Lockout
What You Can Check
- •Check gas supply
- •Verify power supply
- •Look for fault history
Error Code b0
Low System Pressure
What You Can Check
- •Check pressure gauge
- •Look for visible leaks
- •Pressure should be 1-2 bar
Error Code F20
Safety Shutdown - Overheat
What You Can Check
- •Turn off unit immediately
- •Check pump operation
Error Code F22
Low Water / Dry Running
What You Can Check
- •Check system pressure
- •Look for leaks
Don't See Your Error Code?
Viessmann has many error codes across different models. Our technicians are trained on all Viessmann systems and can diagnose any error code.
Call 778-909-5731