176
Measures
Check the expansion vessel.
A.62 PWM signal, heating circuit pump, heating/cooling circuit 1
A.62
System characteristics
No scanning possible for secondary pump/heating cir-
cuit pump, heating/cooling circuit 1
Cause
Lead break, PWM signal, secondary pump/heating cir-
cuit pump, heating/cooling circuit 1
Measures
1. Isolate the system from the power supply. Wait at
least 2 min. Switch on the system.
2. If the message appears often: Replace secondary
pump/heating circuit pump, heating/cooling circuit 1.
A.63 PWM signal, heating circuit pump, heating/cooling circuit 2
A.63
System characteristics
No scanning possible for heating circuit pump, heating/
cooling circuit 2
Cause
Lead break, PWM signal, heating circuit pump, heat-
ing/cooling circuit 2
Measures
1. Isolate the system from the power supply. Wait at
least 2 min. Switch on the system.
2. If the message appears often: Replace heating cir-
cuit pump, heating/cooling circuit 2.
A.65 Heating circuit pump for heating/cooling circuit 2 running dry
A.65
System characteristics
No room heating/room cooling, heating/cooling cir-
cuit 2
Cause
Heating circuit pump, heating/cooling circuit 2 running
dry.
Measures
Fill system and vent.
A.66 Heating circuit pump for heating/cooling circuit 1 not running
A.66
System characteristics
Secondary pump/heating circuit pump, heating/cooling
circuit 1 not running.
Cause
■
No PWM signal, secondary pump/heating circuit
pump, heating/cooling circuit 1
■
Incorrect circulation pump installed
Measures
Use only spare parts supplied or approved by
Viessmann.
Messages
Warning messages (cont.)
6218234
Diagnosis
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