Trouble Shooting Flow Chart (Furnaces Equipped With Fan Control Module Board) - Suburban DD-17DSI Service Manual

SUBURBAN RV FURNACE with FAN CONTROL MODULE BOARDS
T herm ostat C loses
Yes
B lower is operating
at call for heat.
Yes
M otor is operating
Yes
A fter 15 seconds the m odule
creates spark and opens valve.
Yes
S park occurs for approxim ately
7 seconds and m ain burner flam e
establishes.
Yes
T herm ostat opens and the m odule board
operates the fan for the
cool down cycle.
Yes
S ystem O k
TROUBLE SHOOTING GUIDE
12 VDC HEATING SECTION
C heck therm ostat wire connections,
-N o- contact points and the heat
anticipator.
N o
C heck 12vdc at blue wire, check the
am p draw to therm ostat.
N o
C heck for shorts.
C heck com ponents am perage.
Yes
C heck for 12vdc at furnace
Yes
C heck fuse or circuit breaker
Yes
-N o- C heck for 12vdc at power term inal on
m odule board and for 12vdc to red wire
leading to the m otor.
Yes
C h eck ground w ire on term inal block.
-N o- R eset therm ostat. Motor operating. C heck
for 12 vdc at blue wire on m olex edge
connector.
C heck for 12vdc between red and
-N o-
yellow wires at the m odule board.
N o
C heck for 12vdc at lim it switch,
both sides.
N o
C heck for 12vdc at sail switch
both sides.
-N o- N o spark at the electrode
Yes
C heck for 12vdc at gas solenoid
valve.
Yes
D id the gas valve open.
Yes
C heck for restriction in
com bustion air Intake (wasps, etc.)
N o
Is flam e established.
-N o-
R eplace the m odule board
-Yes-
-Yes-
-Yes-
-N o-
-N o-
-N o-
-N o-
-Yes-
-Yes-
-Yes-
-Yes-
-N o-
-N o-
-N o-
-N o-
28
C lean points, secure loose
connections, replace therm ostat if
anticipator is shorted.
R eplace therm ostat.
R epair or replace connections or parts
w ith higher than norm a l am p d ra w.
C heck on/off switch on furnace
R eplace fuse/R eset breaker.
R eplace the m odule board
after confirm ing m otor operation.
R eplace the m otor.
V erify voltage thru lim it and sail switch to
m odule board. If circuit rem ains open for 30
seconds, m odule board will go into lockout and
shut down m otor. R eset therm ostat. R eplace
defective part.
C heck plug connection to the
m odule-electrode and w ire-spark gap 1/8 inch
between probe and ground.
R eplace the sail switch.
R eplace the lim it switch.
R eplace the m odule.
R eplace the m odule.
C heck gas pressure at the m anifold or for
restrictions in the burner orifice.
N o
R eplace the gas valve.
C heck flam e contact to electrode. Flam e should
be hard blue.