Bosch ZSB18 - 2A Installation And Servicing Instructions page 62

62 | Fault finding and diagnosis
Blue light Lockout
indication reset button
Slow flash Flashing
(mostly (reset
off, required)
flashes
on)
Slow flash Flashing
(mostly (reset
on, required)
flashes
off)
Fast flash Off
2 pulses No light
5 pulses No light
Tab. 28
6 720 646 195a (2010/11)
Fault Possible solution/check
Ignition lockout B Gas present and at correct pressure?
B Gas valve
– Check that there is 35V d.c. to each solenoid
– Check the resistance of each solenoid:
Top solenoid = 380 Ω ± 10% (342 - 418 Ω)
Bottom solenoid = 190 Ω ± 10% (171 - 209 Ω)
B Combustion CO
B Flue condition.
– Blocked flue?
B Blocked condensate pipe or frozen condensate.
B Gas valve adjustment.
B Ignition electrodes/harness/connections.
– Check for condition and continuity
B Otherwise replace control board
Flue overheat B Heat exchanger baffles removed and not refitted.
Volatile lockout B Temperature sensors
-
– Check condition and continuity of leads/sensors
Fan does not
B Fan
run
– 230V a.c. across the live (purple) and neutral (brown)
B Fan lead
– Check continuity
B Code plug
– Is code plug missing or not inserted properly.
Not a fault code Service mode selected to minimum, press service button to
return to normal
Not a fault code Service mode selected to maximum, press service button to
return to normal
level.
2
AU/NZ