Worcester Bosch CDI Highflow Combi Boiler Error Codes

Worcester Bosch CDI Highflow Combi Boiler Error Codes

A light on your boiler will flash to indicate that there is a fault. Depending on the type of fault, the light will flash in a different sequence.

There will be 4 quick flashes followed by a 5 second gap when the light is off and finally a series of longer flashes. The number of long flashes tells you which fault the boiler has.

Fault Description System Behaviour
Light off No boiler demand
Light on Heating demand on boiler is OK
1 flash 5 seconds off No ionisation detected after ignition
2 flashes 5 seconds off Loss of ionisation signal during operation
3 flashes 5 seconds off Gas valve error
4 flashes 5 seconds off First safety timing error / ignition timing error
5 flashes 5 seconds off Ionisation detected after burner stopped
Gas valve EV2 leak test failed
Gas valve EV1 leak test failed
Ionisation current detected before burner start
Gas valve error
Ionisation sensor shorted
4 flashes 5 second gap 1 long flash Sensor test failed
4 flashes, 5 second gap, 2 long flashes Safety temperature too high
4 flashes, 5 second gap, 3 long flashes Max safety thermostat activated
4 flashes, 5 second gap, 4 long flashes Return temperature too high
4 flashes, 5 second gap, 5 long flashes Flow temperature too high – supply sensor exceeded 110°c
1 long flash, 4 quick flashes, 5 second gap, 1 long flash, 4 quick flashes Heating control module (HCM) defective
2 long flashes, 4 quick flashes, 5 second gap, 2 long flashes, 4 quick flashes Fan running too fast
Fan running too slow
No airflow after defined period of time
Fan not running
3 long flashes, 4 quick flashes, 5 second gap, 3 long flashes, 4 quick flashes Mains voltage interrupted after locking error
4 long flashes, 4 quick flashes, 5 second gap, 4 long flash, 4 quick flashes Internal control board faults
5 long flashes, 4 quick flashes, 5 second gap, 5 long flash, 4 quick flashes All other miscellaneous faults – reset the boiler by turning the control knob anti-clockwise to the reset position

Leave a Comment

Scroll to Top