Viessmann VITOTRONIC 200 Service Instructions Manual page 42

Troubleshooting
Messages
(cont.)
Message
Code/system characteris-
tics
3A Evaporator temp.sensr
The air discharge tem-
perature sensor is used
for defrosting the evapo-
rator.
40 Flow sensor HC2
Mixer heating circuit M2
is closed.
41 Flow sensor HC3
Mixer heating circuit M3
is closed.
42
Cause
Lead break, evaporator
temperature sensor.
Short circuit, flow tem-
perature sensor in heat-
ing circuit with mixer M2.
Short circuit, flow tem-
perature sensor in heat-
ing circuit with mixer M3.
Measures
Check resistance (Pt 500)
at plug-in connection F17
or terminals X6.4/X6.5
(see page 172); replace
sensor if required.
Check flow temperature
sensor; replace if
required.
■ With a directly control-
led mixer motor:
Check resistance
(Ni 500) at plug-in con-
nection F12 (see
page 172).
■ In the case of control
with extension kit for
heating circuit with
mixer:
see installation instruc-
tions, extension kit.
Check sensor and replace
if required (see installation
instructions, extension kit
for heating circuit with
mixer).