Bradford White UCG100H399, Service Manual

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S er vi ce P roce du re I :
80
High Limit ( Overheat
C ondition )
x C heck the wiring f rom the sensor to the contro l modu l e .
x
M easure the resistance o f each outside wire to the center wire .
x I f either outside wire has a much di ff erent resistance reading , rep l ace
the sensor .
x M ake sure the sensor is secure l y he l d inside the we ll with the c l ip .
x
I f the pro b l em persists and the sensor and wiring check O .K. , then
rep l ace the contro l modu l e .
9 3
D HW/ T E M P
S ensor F au l t
x
C heck the sensor wire harness f rom the sensor to the contro l modu l e .
x M ake sure there are no l oose connections to the contro l p l ug .
x C heck the resistance reading f rom each o f the outside wires to the
center ( common ) wire .
x I f the ohm readings are not f air l y c l ose , rep l ace the sensor .
x
R ep l ace the contro l modu l e i f the pro b l em persists and the sensor and
wire connections are not de f ective .
1 0 5
Fl ame detected out o f
sequence
x C heck to see i f f l ame is present inside the com b ustion cham b er b e f ore
or a f ter the ignition cyc l e .
x I f so , check to make sure the gas va l ve is wired correct l y .
x C heck f or vo l tage at the gas va l ve connection .
x
R ep l ace the gas va l ve i f de f ective .
x I f no f l ame is visi b l e outside o f the ignition sequence/run cyc l e , then
make sure the f l ame sensor is wired to the correct termina l.
x M ake sure the ignition ca b l e is not crossing the f l ame sensor wire or
ignition ground wires .
x I f pro b l em persists and a ll other checks have b een veri f ied , rep l ace the
contro l modu l e .
11 0
I gnition F ai l ure
Occurred
x B urner f ai l ed to l ight or stay l it a f ter 3 retries .
x
Ho l d condition – wi ll reattempt ignition a f ter 1 5 minute waiting period .
x C heck gas va l ve wiring and gas va l ve operation during the ignition
cyc l e .
x I f b urner l ights b ut quick l y goes out , check the f l ame sensor wire or the
f l ame sensor .
x I f the f l ame sensor rod is b ad l y corroded with deposits , c l ean with
sandpaper or rep l ace .
x C heck the in l et gas supp l y to make sure the pressure is su ff icient and
does not drop a f ter the gas va l ve opens .
x M ake sure the com b ustion b l ower is operating during the ignition and
run cyc l e .
x C heck the venting system to make sure the in l et and exhaust termina l s
and venting system is not b l ocked .
1 22
Light - o ff R ate P roving
F ai l ed
x I f b l ower speed is not veri f ied f rom the P W M (P u l se Width M odu l ation )
signa l within 5 minutes , the previous l y descri b ed error code “6 2 ”
changes f rom a ho l d condition to this l ockout code condition .
x
C heck the harness and pin termina l s f or a good connection to the
contro l modu l e .
x
R ep l ace the contro l modu l e i f the wire harness is good .
1 37
I L K Open
( I nter l ock Open )
x C heck i f b l ocked vent sa f ety switch is open .
x
I f switch checks O .K. , rep l ace contro l modu l e
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