Rinnai FUA-E, Service Manual, Page: 30 / 67

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If it is correct unplug the HT lead and hold it about 3 – 5 mm from a clean, earthed,
screw head.
WARNING: ISOLATE THE GAS SUPPLY. KEEP HANDS WELL AWAY
FROM THE END OF THE LEAD – VERY HIGH VOLTAGES . Power the heater and
turn the water on. A spark should jump from the lead to the earthed screw.
If this does not happen replace the sparker box – after you have confirmed voltage
between the grey wires onto the sparker box.
If this does happen, but the electrode will not spark when the HT lead is connected then
visually inspect the electrode, clean it, set the gap, or replace it as described in the first
paragraph under B.
C. Flame Rod.
If the flame rod circuit is faulty the error code will be either 11 or 72.
If 72 is the error disconnect flame rod and cycle unit. If it is 72 again then refer to section
on hot water temperature thermistor. If 72 is not displayed, check for electrical current
leaks, and continue with this section.
First check to make sure all connections are tight. If not, tighten them and adjust the
flame rod.
The next check to be carried out is continuity between the terminal of the flame rod and
various points at the sensor end. Check this while holding the ceramic insulator. As the
flame rod is metal the continuity should be very good throughout the whole length. If the
continuity is not strong then clean the flame rod with steel wool or emery cloth until there
is continuity through the whole length of the flame rod.
With the unit in standby measure the voltage (AC) between the flame rod connection
spade (that is the yellow wire spade connector) to earth. This can be done with the unit
in standby (electric ON) or with the unit on and burning. If it is burning this test will cause
the unit to lockout so the reading will only be brief.
FR – Earth
55 – 150 Vac (running) appx 85 Vac (standby)
If there is no voltage, replace PCB
The next check is the current between the flame rod yellow wire and a clean, earthed
screw with the unit in standby. Current should be at least 1 micro (µ)Amp AC. If it is
less than this replace the pcb.
Next check the current between the flame rod and the pcb. This is measured by placing
the meter in line between the flame rod and the pcb. Unplug the connector at the flame
rod and put one meter lead on the spade, and one in the spade connector.
Current should be at least 1 micro (µ)Amp DC
If current is less than this the flame rod is faulty or needs cleaning.
Diagnostic Checks