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If the tankless unit is properly connected to water, gas, and power supplies but the fan motor does not
initiate when water is run through it, the flow sensor is most likely not working properly and not telling
the PC Board to initiate.
1) TOOLS ‐ Gather the following materials together:
Degreaser in a pump action bottle
a.
#2 Philips Screw Driver
b.
Flashlight
c.
Old Towels, at least three
d.
2) PREPARE THE UNIT ‐ Drain the unit by following the procedures
on p. 22.
3) FRONT COVER ‐ Remove the front cover of the unit. It is held on
by three screws on the top corners and bottom center.
4) DISCONNECT FROM WATERWAY
The flow sensor is located below the water control valve, on
a.
the front leg.
Remove the waterway clips below and above the flow sensor
b.
by pushing on the tabs to pop them off, one on each side of
the flow sensor.
5) CHECKING THE FLOW SENSOR
Check for functionality. Flow rate is determined by an impeller that spins as fluid runs through
a.
it.
Blow into the inlet of the flow sensor. Listen for the spinning impeller; it should spin freely for a
b.
few seconds. If it comes to rest abruptly or doesn't spin at all, it needs to be cleaned or
replaced.
Place the flow sensor into a container of lemon juice or another degreaser for 30 minutes and
c.
check the spinning capability again.
Test the cleaned flow sensor by "jumping" the system:
d.
i. Reattach the flow sensor wires.
ii. Turn power back on to the unit. (GAS SHOULD STILL BE OFF)
iii. Blow into the flow sensor; if the fan initiates, the flow sensor successfully read
6) REASSEMBLE ‐ Reassemble the unit in reverse order. Ensure that the O‐rings and waterway clips are
all in place.
CHECKING THE FLOW SENSOR
the airflow and should now work properly.
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Page
Troubleshooting Guide
Flow sensor
Figure 40
Clips
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