Worcester 28Si Installation And Servicing Instructions page 37

Is the multiway
No
connector at board
position ST16 pushed
fully home on to the
board?
Yes
Check the DHW
No
sensor. Is it correctly
fitted onto the pipe
with heat conductive
paste between the
pipe and sensor?
Yes
Remove multiway
connector from board
position ST16. Test
No
resistance across
contacts 17 and 18
(yellow wires). Is it
between 1 kohm and
30 kohm?
Yes
Test resistance across
No
contacts 12 and 13
(red wires). Is it
between 1 kohm and
30 kohm?
Yes
Test resistance across
No
contacts 7 and 8
(brown wires) and 9
and 10 (violet wires).
Are both readings
below 200 ohms?
Yes
Replace control board.
(Section 15.4.10).
Push fully home
Re-fix sensor onto pipe
No
Is there continuity
from contacts 17 and
18 to DHW sensor?
Yes
Check or replace
DHW sensor.
(Section 15.4.17).
No
Is there continuity
from contacts 12 and
13 to CH sensor?
Yes
Check or replace CH
sensor.
(Section 15.4.15).
Remove both brown
connectors from
No
gas valve.
Is there continuity
from brown and violet
wires to the multiway
connector?
Yes
Replace gas valve.
(Section 15.4.1).
37
Repair or replace
harness.
Repair or replace
harness.
Repair or replace
harness.