Viessmann Vitocrossal 300 Service Instructions For Contractors page 106

Troubleshooting
Repairs
(cont.)
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10
8
6
-20 -10 0
Temperature in °C
1. Pull plug "X3" from the control unit.
Checking cylinder temperature sensor
106
10 20 30
5
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 test on
the sensor itself.
4. Subject to result, replace the lead or
the outside temperature sensor.
1. Cylinder temperature sensor
Pull plug % and measure the resist-
ance.
2. Check the sensor resistance and
compare it with the curve.