Fault Finding - Baxi Combi 105 HE Installation & Servicing Instructions Manual

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 15.0 "Illustrated Wiring Diagram" for position of numbered terminals
Central Heating - Follow operational sequence
Turn selector to
neon illuminated
YES
Turn thermostat
to max.
Pump runs
YES
Primary flow switch operated
YES
Fan runs at max speed
YES
Air pressure
switch proved
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
48
© Baxi Heating UK Ltd 2007
NO
Go to section 'A'
neon flashing
Go to section 'B'
YES
External controls and, where
NO
fitted, integral timer calling for
heat
NO
neon flashing
Go to section 'C'
NO
neon flashing
NO
neons flashing
Go to section 'D'
NO
neon flashing
Go to section 'E'
NO
neon flashing
NO
Replace PCB
NO
Go to section 'F'
YES
neon flashing
Go to sections 'I' & 'L'
NO
Go to section 'G'
YES
Fan stops
16.0
Ensure controls are set to
NO
demand and verify the
contacts are closed
Turn selector to reset
position. If regular resetting is
YES
required or appliance still
does not operate
investigation is necessary
Turn selector to the reset
YES
position. If the neon does not
extinguish go to sections H &
K
YES
Pump stops

Fault Finding

NOTE: When instructed to turn the
selector to the reset position turn the
selector switch fully anticlockwise against
the spring pressure to 'Reset' position and
hold for 2 seconds to reset the boiler.
Go to sections 'J' & 'M'
YES
Operation sequence correct