Rinnai FUA-E, Service Manual

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A. Combustion Fan Circuit.
The voltages should be checked while the unit has the electric power On. The meter
leads can be inserted into the connection plug at the pcb (Plub B from wiring diagram.)
To test the resistances electrically isolate the water heater, unplug the connector either
at fan motor (B1) or at pcb (B), and measure the resistances through the motor.
Red – Black
6 – 40 Vdc -- fan must be on do not check Resistance
White – Black 2 – 10 Vdc -- fan must be on appx 8.2 kOhms
Yellow – Black 11 – 13 Vdc -- standby or run appx 2.5 kOhms
If Black – Red (Drive Power) voltage incorrect (while the fan should be running) replace
pcb.
If Yellow – Black (Control Power / Speed) voltage is incorrect replace the pcb
If Yellow – Black resistance is incorrect replace the fan motor
If White – Black (Fan proving) voltage or resistance is incorrect replace the fan motor.
If the water heater is very loud and shaking the combustion fan may not be installed
properly. Make sure it is in properly.
To remove the combustion fan assembly first remove the hot water outlet pipe
connection, pull out the pipe and bend it out of the way. Then remove the 4 screws from
the air outlet duct (2 in front, one each side) and take the fan out the left side of the
heater.
B. Ignition System.
The best check for the ignition electrode and sparker is to listen to the unit for the ticking
sound as it sparks. If it is ticking the sparker sub pcb is working. Remove the electrode
and visually inspect for damage. Be sure to check the burner where the electrode should
spark to. The spark will travel to the cleanest place so if the burner is rusty the spark
could travel back to the plate. Give the burner a good clean with wire wool or something
abrasive.
Check the thick black HT lead from the sparker box to the electrode. Be sure that
connections on both ends are tight and the lead has not been damaged. Measure the
resistance through the wire if it looks as though it may be damaged. The resistance
should be very low.
Sparker box / sub pcb
Test to make sure that the sparker is getting a signal from the pcb through the two grey
leads from the sparker to the pcb. The voltage can be measured at the terminals at the
sparker by loosening the connector plug and putting multimeter leads on the terminal
connectors. Put the meter leads on the terminals, power the heater, then turn on the
water. It will only give a quick voltage reading.
Grey – Grey
240 Vac.
If this is not correct replace the pcb.
Diagnostic Checks