Fault finding and diagnosis
57
Bosch Condens 5000W – 6 720 646 195 (2018/10)
Table 20 Fault finding guidance
Slow flash
(mostly OFF,
flashes ON)
Flashing (reset
required)
Ignition lockout ▶ Check gas is present and at the correct pressure.
▶ Check gas valve:
– Check that there is 29V d.c. to each solenoid
– Check the resistance of each solenoid:
Top solenoid = 380 ± 10% (342 - 418 )
Bottom solenoid = 190 ± 10% (171 - 209 )
– Gas valve adjustment.
▶ Check combustion CO
2
level.
▶ Check flue condition, ensure the flue is not blocked or restricted.
▶ Check for blocked condensate pipe or frozen condensate.
▶ Check condition and continuity of ignition electrodes/harness/connections.
▶ Otherwise replace control board
Slow flash
(mostly ON,
flashes OFF)
OFF Flue overheat Flue temperature too high
▶ Check heat exchanger baffles are correctly fitted or removed and not refitted
Heat exchanger
overheat
▶ Check:
– Water pressure.
– All air is vented.
– Pump/harness/connections.
– Water leaks/blockage.
– Safety thermostats/low voltage wiring harness/connections.
– Blocked heat exchanger.
▶ Otherwise replace control board
Fast flash OFF Volatile lockout
(sensor fan or code
plug)
▶ Check:
– Temperature sensors:
Condition and resistance of the leads.
– Fan.
230V A.C. across the live (purple) and neutral (brown)
Fan lead continuity.
– Code plug.
Is code plug missing or not inserted properly?
2 pulses No Light Not a fault code Service mode selected to minimum.
▶ Press service button to return to normal.
5 pulses No light Not a fault code Service mode selected to maximum.
▶ Press service button to return to normal.
Blue light
indication
Lockout reset
button
Fault Possible solution/check
To Next Page
Loading...
