Viessmann Vitodens 242-F Installation And Service Instructions Manual page 102

Troubleshooting
Maintenance
(cont.)
200
100
80
60
40
20
10
8
6
-20 -10 0 10 20 30
Temperature in °C
Fig. 67 Sensor type: NTC 10 k
102
Ω
1. Pull plug "X3" from the control unit.
2. Test the resistance of the outside temperature sen-
sor across terminals "X3.1" and "X3.2" on the dis-
connected plug and compare it with the curve.
3. Where actual values deviate severely from the
curve values, disconnect the wires at the sensor
and repeat the test on the sensor itself.
4. Depending on the result, replace the lead or the
outside temperature sensor.