Viessmann Vitoclima 300-S Service Instructions For Contractors page 18

Troubleshooting
Diagnosis
(cont.)
No. Fault code
5 4 3 2
20
21
...
24
25
26
27
28
29
30
31
Cooling and heating LEDs illumi-
nate together
Only the heating LED illuminates
Diagnosis at the external unit, type OD306H
The MSMP controller is equipped with 9 LEDs (1 standby LED, 3 equipment
LEDs and 5 fault LEDs).
18
Fault
1
Overtemperature cut-
out of the heat exchan-
ger of the internal de-
vice
Overrun protection
(N/A)
EEPROM not updated
EEPROM faulty
Poor communication
Utilisation of EEPROM
data
Model A
Model B
Model C
Model D
Cause/Remedy
Unit operates with ROM
parameters; no change of
the unit settings (fan, tem-
perature etc.) possible.
Replace the controller of the
internal device.
Check the electrical con-
necting cable between the
internal device, the external
unit and earth
No fault