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© Baxi Heating UK Ltd 2009
16.0 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),
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 13.1 “Illustrated Wiring Diagram” for position of numbered terminals
Central Heating - Follow operational sequence
Turn selector to
neon illuminated
Primary flow switch operated
Fan runs at max speed
Burner goes out
Turn thermostat
to max.
Pump runs
Air pressure
switch proved
illuminated
Burner on neon
illuminated
Burner output
modulates until set
temperature is reached
Spark at ignition electrodes
for up to 10 seconds
Go to section ‘A’
Go to section ‘B’
Go to section ‘C’
Go to sections ‘J’, ‘L’ & ‘D’
Go to section ‘E’
Replace PCB
Turn selector to the reset
position. If the light does not
extinguish go to sections
H & K
Go to section ‘F’
Go to section ‘I’
Go to section ‘G’
Fan stops Pump stops
Operation sequence correct
Turn the selector switch to
the ‘Reset’ position and hold
for at least 2 seconds. If
regular resetting is required,
or appliance still does not
operate, investigation is
necessary
External controls and, where
fitted, integral timer calling for
heat
Ensure controls are set to
demand and verify the
contacts are closed
Burner extinguishes
after 10 seconds
YES
YES
YES
YES
YES
YES
YES
YES
YES
NO
YES
YES YES YES
NO
NO NO
NO
NO
NO
NO
NO
NO
YES
NO
NOTE: When instructed to turn the Selector to
the reset position turn the Selector Switch fully
anticlockwise against the spring pressure and hold
for 2 seconds to reset the boiler.