Viessmann Vitotronic 100 GC1 Installation And Service Instructions Manual page 104

Troubleshooting – Vitotronic 300-K, MW1S
Faults displayed at the programming unit
Fault
System characteristics
code
d d d d a a a a Control mode without room
influence
d d d d b b b b
d d d d c c c c
d d d d d d d d
d d d d e e e e
d d d d f f f f
104
(cont.)
Cause
Short circuit
Room temperature sensor,
System circuit A1
Short circuit
Room temperature sensor,
Mixing valve circuit M2
Short circuit
Room temperature sensor,
Mixing valve circuit M3
Open circuit
Room temperature sensor,
System circuit A1
Open circuit
Room temperature sensor,
Mixing valve circuit M2
Open circuit
Room temperature sensor,
Mixing valve circuit M3
Remedy
Check room temperature sensor
(see page 139) and DIP switch on
Vitotrol (see page 130 and 132) Vitotrol (see page 130 and 132)