Viessmann MPA51 Operating And Service Instructions page 14

Diagnosis
Diagnosis
(cont.)
General process errors
Fault Display
*1
code
F AA F AA
F AA F AA
F Ab F Ab
F Ab F Ab
F Ab F Ab
F Ad A
F AE F AE
F AF F AF
F A0 and F A0 and
F A1 F A1
All fault codes are saved to the fault memory and the last 10 can be called up.
*1
14
System charac-
teristics
Fan pressure de-
velops during the
air pressure switch
idle state check
Air pressure
switch contact is
not in the idle
state
Air pressure
switch shows no
air pressure, fan
not running
Air pressure
switch switches off
during operation
Fan not running
Gas pressure
switch reports no
gas pressure
Burner control unit
in fault state
Burner control unit
in fault state
Status duration
too long, fan ramp-
up
Cause
Wind influence on
fan
Air pressure
switch faulty
Air pressure
switch is faulty, in-
correctly connec-
ted or incorrectly
set
Flue gas back
pressure, conden-
sate banked up
Fan faulty; cables
are faulty or bro-
ken
Gas shut-off valve
closed, gas pres-
sure switch faulty
Valve 1 leaking
Valve 2 leaking
Internal fault; fan
cannot reach its
set value
Measures
Check flue outlet
(chimney)
Replace air pres-
sure switch
Replace air pres-
sure switch, con-
nect correctly or
adjust setting
Remove flue gas
back pressure,
check for banked
up condensate, re-
set burner control
unit
Check cables; re-
place fan if re-
quired
Open gas shut-off
valve, check gas
flow pressure,
clean gas filter if re-
quired
Replace the gas
train
Replace the gas
train
Replace burner
control unit or fan