Benchmark ZWB 7-29 CC1 Installation And Servicing page 76

Failure identification procedure
E2
flashing.
The heating outlet NTC sensor is damaged.
Check
1.
B Press button
B Select service function .1 .
Is a temperature between 0. and
5. displayed?
2. Temperature for heating outlet NTC
sensor between 95. and 99. is dis-
played.
3. Check if the 20-pin connector lead
assembly is damaged.
4. The PCB control board is damaged.
28
yes:
.
no:
yes:
no:
Action
B Note the setting of the temperature controls
and .
The heating outlet NTC sensor is in short circuit:
B Power OFF the appliance.
B Replace CH flow NTC sensor; observe fitting
instructions for NTC sensor when doing so.
B Turn ON the appliance.
E2? ↓2.
↓2.
The CH flow NTC sensor is interrupted :
B Power OFF the appliance.
B Replace CH flow NTC sensor; observe fitting
instructions for NTC sensor when doing so.
B Turn ON the appliance.
E2? ↓3.
↓3.
B Power OFF the appliance.
B Disconnect the boiler electrical connection.
B Change the 20-pin connector lead assembly.
B Reconnect the boiler electrical connection.
B Turn ON the appliance.
E2? ↓4.
B Make a note of the altered service settings (see
table 1, "First Service Level; Values that can be
modified" at page 8 and table 5, "Secondary
Service Level; Values that can be modified" at
page 11).
B Power OFF the appliance.
B Disconnect the boiler electrical connection.
B Change PCB control board.
B Reconnect the boiler electrical connection.
B Turn ON the appliance.
B Restore service settings previously noted down.
7 181 465 346 GB (03.02)