Viessmann VITODENS 333-F WS3A Service Instructions Manual page 84

Troubleshooting
Repairs
(cont.)
1. Boiler water temperature sen-
sor
Pull the leads off the boiler tem-
perature sensor and check the
resistance.
Cylinder temperature sensor
Pull plug % from the cable har-
ness at the control unit and check
the resistance.
Flow temperature sensor
Pull plug "X3" from the control
unit and check the resistance
across terminals "X3.4" and
"X3.5".
Checking the outlet temperature sensor
84
2. Check the sensor resistance and
compare the actual values with the
curve.
3. Replace the sensor in case of
severe deviation.
Danger
The boiler water tempera-
ture sensor is immersed in
the heating water (risk of
scalding).
Drain the boiler before
replacing the sensor.
1. Pull the leads from outlet tempera-
ture sensor A.
2. Check the sensor resistance and
compare it with the curve.