0020308121_04 Installation and maintenance instructions 87
Code/meaning Possible cause Measure
N.096
The gas valve stepper motor
has reached the maximum per-
missible step number.
Air-mass flow sensor dirty or
defective (only in conjunction
with the conversion set compris-
ing the air intake pipe with in-
tegrated non-return valve and
air-mass flow sensor)
1. Check the air-mass flow sensor for dirt.
2. If required, replace the entire air intake pipe.
N.097
The air ratio is too low.
Fault in the flue gas route
caused by recirculation or flue
gas blockage
▶ Check the entire flue gas route.
Condensate discharge pipe
blocked
▶ Check the condensate discharge pipe.
Gas flow pressure too low ▶ Check the gas flow pressure and the external gas pressure
switch.
Incorrect gas type set ▶ Check the gas type and the gas type setting under D.156 and
D.157.
Gas valve assembly offset in-
correctly stored in D.052 und
ggf. D.182
▶ Check the offset setting for the gas valve assembly.
Fault in the electrical connection
for the gas valve assembly
▶ Check and, if required, replace the wiring harness for the gas
valve assembly.
Gas valve assembly not elec-
trically connected/incorrectly
connected
▶ Check the electrical connection to the gas valve assembly.
Control electrode defective ▶ Check and, if required, replace the control electrode.
PCB defective ▶ Replace the PCB.
Fan defective ▶
Check and, if required, replace the fan.
Air-mass flow sensor dirty or
defective (only in conjunction
with the conversion set compris-
ing the air intake pipe with in-
tegrated non-return valve and
air-mass flow sensor)
1. Check the air-mass flow sensor for dirt.
2. If required, replace the entire air intake pipe.
N.100
The signal for the outdoor tem-
perature sensor has been inter-
rupted.
Outdoor temperature sensor not
connected
▶ Check the settings on the control.
Outdoor temperature sensor
defective
▶ Check the outdoor temperature sensor.
Outdoor temperature sensor not
installed
▶ Deactivate the weather-compensated control using D.162.
N.144
The ionisation signal for the
control electrode is too low. The
drift adaptation has failed again.
Fault in the flue gas route
caused by recirculation or flue
gas blockage
▶ Check the entire flue gas route.
Condensate discharge pipe
blocked
▶ Check the condensate discharge pipe.
Gas flow pressure too low ▶ Check the gas flow pressure and the external gas pressure
switch.
Incorrect gas type set ▶ Check the gas type and the gas type setting under D.156 and
D.157.
Control electrode defective ▶ Check and, if required, replace the control electrode.
Gas valve defective ▶ Replace the gas valve.
PCB defective ▶ Replace the PCB.
Interruption in the wiring har-
ness
▶ Check the wiring harness including all plug connections and, if
required, replace it.
N.194
The power supply unit for the
PCB is defective.
Power supply unit for the PCB
is defective
▶ Replace the PCB.
N.270
The temperature spread via
the secondary heat exchanger
(heating flow – domestic hot
water connection) is too high.
The unit switches from regulat-
ing to controlling until the cause
has been eliminated by cus-
tomer service.
Strainer at cold water inlet dirty ▶ Check the strainer at the cold water inlet for dirt, clean it and, if
required, replace it.
Cold water adjusting valve not
installed (only on a product with
no factory-installed flow rate
limiter)
▶ Install the cold water adjusting valve.
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