l
~
~
Does burner light?
+
YES
+
Go to 6
@J
t¥J Vaillanl
!~O~
I
HEATING,CONTROLS,HOTWATER.
(a) Check variable
potentiometer (boiler stat)
setting on maximum.
(b) Check appliance not in
time delay (isolate power wait
5 seconds and restore).
(c) Check Domestic Hot
Water overheat thermostat
(VCW only) - pull off bottom
white wire, if burner lights -
Replace DHW overheat.
Refer to Pic 7.
(d) Check NTC - (pull wire off
NTC sensor, if burner lights
change NTC. Refer to Pic 8.
(e) Check operation and
adjustment of microswitch M2
20v DC (VCW only).
Refer to Pic 15.
(f) Check differential valve
closes microswitch M4 20v
DC (VC only).
T
(9) Check 20v DC across gas
operator, if available but
operator fails to open (audible
click) change operator.
Refer to Pic 21
(h) Check for continuity
through gas section
microswitch M5 (20vDC)
T Pic38
~
(i) Check for continuity
through main heat exchanger
overheat thermostat.
T Pic39
Pie3?
0) Check small p.c.b. bridge
located bottom rear of Mother
Board.
T
.~
Does burner modulate up to high
fire rateafterapprox5 seconds? I~O"
~
,
YES
,
Go to 7
I
(a) Check standing and
working gas pressure at
appliance inlet. Refer to Pic
25.
(b) Check diaphragm pump
operating tubes and throttle
jet clear. Refer to Pic 26.
(c) Check voltage across
diaphragm pump (approx 6v
DC) (NTC disconnected
Refer to Pic 27.
(d) Check burner pressure
settings low and high fire
rate. Refer to Pic 28.
(e) Check and/or replace
gas operator.
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