Viessmann FB2B Installation And Service Instructions Manual page 118

Troubleshooting
Repairs
(cont.)
20
10
8
6
4
2
1
0.8
0.6
0.4
10 30 50 70 90 110
Temperature in °C
Checking collector temperature sensor or cylinder temperature
sensor on the solar control module
The solar control module is attached to
the l.h. side of the air box.
118
1. ■ Boiler water temperature sensor
Pull the leads from boiler water
temperature sensor A and check
the resistance.
■ Cylinder temperature sensor
Pull plug % from the cable har-
ness at the control unit and check
the resistance.
■ Flow temperature sensor
Pull plug "X3" from the control unit
and check the resistance across
terminals "X3.4" and "X3.5".
2. Check the sensor resistance and
compare the actual values with the
curve.
3. Replace the sensor in case of severe
deviation.
Danger
The boiler water temperature
sensor is immersed in the
heating water (risk of scald-
ing).
Drain the boiler on the heating
water side before replacing
the sensor.