Viessmann VITOLADENS 300-C Service Instructions Manual page 71

Fault codes
(cont.)
Fault code System character-
on the dis- istics
play
FF Burner blocked
Repairs
Checking the outside temperature sensor
Cause Measures
Internal fault Start the equipment
again. Replace the con-
trol unit if the equipment
will not restart.
1. Pull plug "X3" from the control unit.
2. Test the resistance of the outside
temperature sensor across term-
inals "X3.1" and "X3.2" on the dis-
connected plug and compare it with
the curve.
3. Where actual values strongly devi-
ate from the curve values, discon-
nect the wires at the sensor and
repeat test on the sensor itself.
Troubleshooting
71