Fault Finding - Baxi Maxflow Combi FS Installation And Servicing Instrucnion

Refer to Section 12.0 "Illustrated Wiring Diagram"
for position of numbered terminals
Central Heating - Follow operational sequence
Turn selector to
neon illuminated
YES
Turn thermostat
to max.
Is neon illuminated ?
YES
Diverter valve operated
i.e.primary water diverted
to the CH system
YES
Pump runs
YES
Primary flow switch
operated
YES
Fan runs at max speed
YES
Air flow monitor
neon stays off
YES
Spark at ignition
electrodes for up to 10
seconds
YES
Burner on neon
illuminated
YES
Burner extinguishes
after 10 seconds
NO
Burner output
modulates until set
temperature is reached
YES
Burner goes out
YES
Boiler operates correctly,
C.H. remains cold
NO
Go to section 'A'
Electrical supply at
neon PCB
YES
NO
External controls calling
for heat
NO Electrical supply at
diverter valve
YES
Check valve wiring - if OK
replace main PCB
NO
Go to section 'B'
NO
Go to section 'C'
Safety Thermostat
NO
neon illuminated
NO
Go to section 'D'
NO
neon illuminated
NO
Red reset button
illuminated
NO
Go to section 'H'
NO
Go to section 'F'
YES
Go to section 'I'
NO
Go to section 'G'
YES
Fan stops
Check 230V at main PCB
M3 connectors 6,7
NO
Replace main PCB

13.0 Fault Finding

CARRY OUT INITIAL FAULT FINDING CHECKS
1. Check that gas, water and electrical supplies are available at the boiler. Electrical supply =
230V ~ 50 Hz. CH water system pressurised to 0.5 bar when the boiler is cold. The preferred
minimum gas pressure is 19.5mbar (natural gas), 27mbar (butane) or 36mbar (propane).
2. Carry out electrical system checks, i.e. Ground Continuity, Resistance to Ground, Short Circuit
and Polarity with a suitable meter. Note: Repeat these checks after servicing or fault finding.
3. Ensure all external controls are calling for heat and check all external and internal fuses.
Before servicing or replacement of parts ensure the gas and electrical supplies are isolated.
NO
YES
Ensure controls are set to
NO
demand and verify the
contacts are closed
Internal clock (if fitted)
is calling for heat
NO
NO
Replace valve or head
Press white reset button.
If neon stays
YES
illuminated or if boiler
requires regular resetting,
investigation is necessary
YES
Go to section 'E'
YES
Press to reset
YES
Pump continues for
3 minutes
YES
Check continuity of the
wiring
Replace neon PCB
Replace main PCB
YES
Go to section 'L'
Set clock
Go to section 'J'
If still illuminated,
go to section 'K'
YES
Operation sequence
correct
YES
Replace 3-way valve
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