Fault Finding - Baxi Maxflow Combi WM Installation And Servicing Instructions

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: These checks must be repeated after any servicing or fault finding.
3. Ensure all external controls are calling for heat and check all external and internal fuses. Before any servicing or replacement of parts
ensure the gas and electrical supplies are isolated.
Refer to Section 13.0 "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
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
Boiler operates correctly,
C.H. remains cold
38
NO
Go to section 'A'
Replace neon PCB
YES
External controls calling
for heat and if fitted,
NO
internal clock calling for
heat
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

Ensure controls are set to
NO
demand and verify the
contacts are closed
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 to run
YES
Check continuity of the
wiring
Go to section 'J'
If still illuminated,
go to section 'K'
YES
Operation sequence
correct
YES
Replace 3-way valve