Viessmann VITODENS 200-W Installation And Service Instructions Manual page 135

Repairs
(cont.)
Fault "A3" during commissioning
During commissioning, the control unit
checks whether the flue gas temperature
sensor is correctly positioned.
If the flue gas temperature sensor is not
positioned correctly, commissioning is
cancelled and fault message A3 is dis-
played.
1. Check whether the flue gas temper-
ature sensor is correctly inserted.
See previous diagram.
Checking the temperature limiter
If the burner control unit cannot be reset
after a fault shutdown, although the
boiler water temperature is below
approx. 75 °C, check the following:
A
2. If necessary, correct the position of
the flue gas temperature sensor or
replace faulty flue gas temperature
sensor.
3. Press reset button R and repeat com-
missioning.
The check is repeated until it is com-
pleted successfully.
1. Pull the leads from temperature lim-
iter A.
2. Check the continuity of the tempera-
ture limiter with a multimeter.
3. Remove the faulty temperature lim-
iter.
4. Coat the replacement temperature
limiter with heat conducting paste
and install it.
5. After commissioning, press reset but-
ton R on the control unit.
Troubleshooting
135