31
221873B
Check continuity of clock/timer harness, ensure an electrical supply is available at the clock,
ensure that remote controls are calling for heat, ensure the override switch, if fitted, is in overide position.
NB. The clock can be by passed by refitting the plug link which should be inside the clock timer cover.
Isolate electrical supply, set clock to an on period.
Is there continuity across common and heating?
Does clock keep time?
NO
Clock/timer in order if no central heating,
refer to main fault finding.
Set clock to off period. Is there continuity across
common and heating on?
NO
Faulty clock/timer.
Replace.
NO
Faulty clock/timer.
Replace.
Faulty clock/timer.
Replace.
YES
YES
YES
Check continuity of clock/timer harness, ensure an electrical supply is available,
ensure that remote controls are calling for heat.
NB. The clock can be by passed by refitting the plug link which should be inside the clock timer cover.
Isolate the boiler from electrical supply remove outer case.
Disconnect and insulate the cables
from heating common and heating on.
Switch on electrical supply,
is there a display on clock/timer?
NO
Clock/timer in order if no central heating,
refer to main fault finding.
Advance clock/timer until a demand is indicated
Is there now continuity between heating
common and heating on?
YES
Faulty clock/timer.
Replace.
Faulty clock/timer.
Replace.
YES
YES
YES
NO
13 Fault Finding
DIGITAL CLOCK/TIMER FAULT FINDING
Diagram 13.4
7461
7463
Diagram 13.5
ELECTRO/MECHANICAL CLOCK/TIMER FAULT FINDING
YELLOW
YELLOW
ORANGE
PURPLE
(L)
(N)
EXTERNAL
CONTROLS
PLUG FROM CLOCK/TIMER
