Viessmann WB1A007 Installation And Service Instructions Manual page 64

Troubleshooting
Diagnosis
(continued)
Diagnostics table: Faults with fault display on control unit (continued)
Fault mes- System behavior
sage in dis-
play window
f7
Burner blocked
f8
Burner in fault mode
f9
Burner in fault mode
fa
Burner in fault mode
fd
Burner blocked
fe
Burner blocked
18
Burner in fault mode
58
Burner in fault mode
a9
Non-permanent lock-out
(burner in fault mode)
64
Cause
Faulty water pressure sensor
Combination gas valve closes too
late
Blower speed too low at burner start Check the blower, check the blower
Blower not at stand-still (blower
must be in stand-still when in stand-
by mode)
Burner control unit fault
Faulty main PCB
DIP switch S2 is set to "ON"
DIP switch S4 is set to "ON"
Communication error OpenTherm
Module
Corrective measures
Check the water pressure sensor and
the interconnecting cable.
Check the gas combination valve.
Check both air and gas paths.
Press "Reset".
cables and supply, check the blower
control.
Press "Reset".
Check the blower, check the blower
cables, check the blower control.
Press "Reset".
Check the ignition electrodes and
leads. Check whether a strong inter-
ference (EMC) field exists near the
equipment.
Press "reset".
If the fault is not removed, replace
the control unit.
If the equipment will not restart after
resetting, replace control unit
Set DIP switch S2 back to "OFF"
Set DIP switch S4 back to "OFF"
Turn boiler OFF, then ON
Check communication cable on Ter-
minals X3.3, X3.4 on boiler controls.
Check connection on OT-Module sub
base Terminals 12, 13.
Check 24VAC output of PPM of the
boiler Terminals X4.3, X4.4 (RT Ter-
minals).
Check for 0-10VDC input signal (a
min. of 3.0 volts is required to start
up the boiler).