Cleaning The Rod Assembly (Flame Sensor And Air/ Fuel Ratio Rod) - A.O. Smith ATI-140H-N Service Handbook

Figure 17.
Rod
Assembly
Also, if you have a remote,
you can read the fl ow rate
by pushing the "Info" bu on
three mes.
4. Reinstall the flow sensor as
described in "Installation" on page
55.
Cleaning the Rod
Assembly (Flame
Sensor and Air/
Fuel Ra o Rod)
Tools:
●
Sheet of 100 Grit Sandpaper or
other suitable abrasive
●
#2 Philips Screw Driver
●
Flashlight
●
Replacement gasket, part 319143-
034.
1. Disconnect power to your unit
by either unplugging it from the
wall outlet, or by turning it off at
the circuit breaker, depending on
the setup. Verify that power is
off using a volt meter or similar
device.
2. Remove the front cover. It is held
on by two screws on the top and
28 • Condensing Models: On-Demand Water Heater Service Handbook
two screws on the bottom.
3. Remove the rod assembly as
described below. (See Figure 17.)
3.1 Locate the yellow and
orange wires located in the
center of the unit (beside
the sight glass).
3.1 Disconnect these wires.
NOTE: The yellow wire
is locked onto the rod's
conduc ve spade. To
release the spade connector,
pinch the flat surfaces
together at the back of the
connector. (Pinch and pull
at the same me.)
3.2 Remove the three Phillips-
head screws holding the
panel in place.
3.3 Pull the
assembly out.
CAUTION! All
pieces are
separate. Be
careful to
not drop or
lose the sight
glass.
4. Clean the flame
sensor and air/
fuel ratio rod as
described below.
IMPORTANT: Be
gentle with the
sensor rods while
cleaning them
because they can
bend out of place
easily. To function
properly, their
position relative to
the burner must be
unaltered.
4.1 Clean the flame sensor
thoroughly with 100 grit
sandpaper or other suitable
abrasive. Con nue un l it
has a bright fi nish.
4.2 Clean the air/fuel ratio rod
with 100 grit sandpaper
or other suitable abrasive.
Con nue un l it has a bright
fi nish.
5. Inspect the ceramic insulator for
chips or cracks. (This ceramic
insulator holds the flame sensor
and air/fuel ratio rods in place.)
Replace it if any chips or cracks are
visible or if either rod moves freely
inside the ceramic.
6. Reassemble the unit in reverse
order: gasket, rods, and metal
Figure 18.
Descaling the Water Heater
On-Demand
Water
Heater
H C
A
B
C D
Pump
Descaling