Viessmann Vitodens 100-W B1HA 26Vitodens 100-W B1HA 35Vitodens 100-W B1KA 35 Installation And Service Instructions Manual page 62

Troubleshooting
Boiler Connection
Start-up and Maintenance
62
(continued)
Vitodens 100-W, B1HA series & B1KA Combi Installation/Service
Check Control unit fuse
1. Switch off main power supply.
2. Flip down control unit.
3. Remove cover A.
4. Check fuse F4 T 2.5A (slow blow).
Replacements fuses are available from Viessmann.
Check DHW outlet temperature sensor (B1KA only)
1. Pull the leads from outlet temperature sensor A.
2. Check the sensor resistance and compare it with
the curve.
3. Replace the sensor in case of severe deviation.
Note: Water can leak when replacing the outlet
temperature sensor. Shut off the cold water
supply. Drain the DHW line and the plate type
heat exchanger (DHW side).
Check DHW tank temperature sensor (B1HA only)
1. Remove plugs
2. Check the sensor resistance and compare it with
the curve.
3. Replace the sensor in case of severe deviation.
Temperature
%
from the cable harness.