Viessmann Vitodens 333 Service Instructions Manual page 85

Repairs
(cont.)
1. Boiler temperature sensor: Pull the
leads from boiler temperature
sensor A and measure the resis-
tance.
Cylinder temperature sensor: Pull
plug % from the cable harness on
the control unit and measure the
resistance.
Flow temperature sensor: Pull
plug X3 from the control unit and
measure the resistance across
terminals X3.4 and X3.5.
2. Check the sensor resistance and
compare actual values with the
curve.
3. Replace the sensor in case of
severe deviation.
Danger
The boiler temperature sen-
sor is immersed in the heat-
ing water (risk of scalding).
Drain the boiler before repla-
cing the sensor.
Troubleshooting
85