Baxi Maxflow Combi WM Installation And Servicing Instructions page 40

Fault Finding Solutions
A
Is there 230V at:
1. Main terminals L and N
2.
Main terminal fuse
3. Both sides of suppressor
4. PCB M6 connector, terminals 18,19
B
1. If pump jammed, release
2. Main PCB M1 connector, terminals 1,2-230V
YES
3.
Change pump supply cable
C
1. CH system pressure 0.5 to 1.5 bar
2.
Check the tap of the automatic
air vent is opened
3.
Primary flow valve diaphragm damaged
D
1.
Continuity across primary flow
microswitch and main PCB M7
connector, terminals 24,25
2.
DHW / primary temp. sensor faulty cold
resistance approx. 11K ohms
(resistance reduces with increase in temp.)
3. Fan connections correct at fan
and ignition PCB
Ignition PCB M2 connector, is
230V across terminals 17,18
E
Ignition PCB M2 connector, is
230V across terminals 17,18
NO
Replace
ignition PCB
F
Gas at burner
40
NO
NO
NO
NO
NO
NO
NO
YES
NO
NO
YES
NO
YES
Check and correct if necessary
1. Electrical and pressure tube connections
2. Blockage of pressure tubes
3. Restriction in flue
4. Venturi
NO
Ensure gas is on and purged
230V at gas valve and across ignition PCB -
M1 connector, terminals 1,2
NO
Flame failure reset button
NO
230V at ignition PCB - M1 connector,
terminals 5,6
NO
Replace ignition PCB
Check electrical supply
Replace fuse
Replace suppressor
Check wiring
Replace pump
NO
Replace main PCB
Re-pressurise system
Check the water valves are opened
Replace diaphragm
Flow valve rod obstructed
Replace microswitch
YES
Replace sensor
Fan jammed or faulty winding
Replace ignition PCB
YES
YES
illuminated
YES
13.0 Fault Finding
NO
neon
illuminated
YES
Replace fan
NO
neon stays off
Replace gas valve
Press to reset
Replace reset button
Replace neon PCB
If problem is not
solved replace
main PCB
Replace air
pressure switch