Buderus Logamax GB062-24 KDE H V2 Service Manual page 26

4
Fault finding
4Y
Flow temperature sensor (CH-NTC) faulty.
Step
1. Check the flow temperature sensor for
damages.
B Switch off the boiler.4C
B Remove the Socket of NTC.
B Measure the electrical resistance of
CH-NTC (in Ω) (see NTC tables).
Is the resistance value correct ?
2. Check the NTC cables for damages.
B Switch off the boiler.
B In case of CH-NTC is changed :
- Remove the NTC socket.
- Measure the NTC resistance.
- Connect the socket again.
B Remove the big socket (20 Pole) on
PCB.
B Measure the NTC resistance (Ω) on
big socket (PCB side).
Are measured resistance values on
NTC and socket side different ?
3. Electronic board (PCB) is defect.
26
Remedy
yes: --> 2.
B Change the Sensor.
no:
B Switch on the boiler.
4Y on display ?
-->2.
yes: B Change the cable haarness.
B Switch on the boiler.
4Y on display ?
-->3.
no: --> 3.
B Switch off the boiler.
B Cut the main voltage supply.
B Change the electronic board (PCB).
B Switch on the main voltage supply.
B Switch on the boiler.
B END
Logamax Plus GB062