Viessmann VITODENS 242-F Installation And Service Instructions Manual page 139

Repair
(cont.)
Checking the outside temperature sensor
X3
200
100
80
60
40
20
10
8
6
-20 -10 0
Temperature in °C
Sensor type: NTC 10 kΩ
1. Pull plug "X3" from the control unit.
10 20 30
2. Test the resistance of the outside
temperature sensor across terminals
"X3.1" and "X3.2" on the disconnec-
ted 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 sen-
sor.
Troubleshooting
139