Viessmann VITODENS 100-W Installation And Service Instructions Manual page 32

Troubleshooting
Repairs
(cont.)
X21 X7
X20
4 3 2 1
100
80
60
40
20
10
8
6
4
-15 -5 0 10 20 30
-10
Temperature in °C
32
1. Open the control unit casing. See
page 11.
2. Disconnect outside temperature sen-
sor leads.
3. Check the sensor resistance and
compare it with the curve.
4. Replace the sensor if the resistance
varies significantly from the figure
shown.