Rinnai INFINITY 26i Service Manual page 30

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.
With the unit running measure the voltage (AC) from the flame rod connection spade (that the
yellow wire with the grey covered spade connector fits on) to earth. Do this with the unit on
and burning. This will cause the unit to lockout so the reading will only be brief. Check the
resistance as well, this should be done with the unit off and the yellow flame rod spade
connector unplugged. Measure the resistance through the flame rod, not the pcb.
FR – E 5 – 150 Vac over 1 M Ohm
If the voltage is correct, replace PCB
If the voltage is incorrect, replace flame rod.
If the resistance is correct, replace the pcb
If the resistance is incorrect, replace the flame rod.
Another check is the current from the flame rod to 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 over 1 micro (µ)Amp
If current is more than this the pcb is faulty.
If current is less than this the flame rod is faulty or needs cleaning.
Infinity 26i and HD50i