andrews Fastflo WHC56 Service Manual page 27

7. Error display 14 immediately after turning
unit ON.
8. Error display 90 or 99 immediately after turning
unit ON.
B. No hot-water supply/combustion.
1. Water flow sensor error.
Inspect overheat prevention device (thermal fuse).
(1) Remove connector 38 on the circuit board and
measure the resistance between Blue 25 and
Blue 31.
2Ω or less
Normal
Yes Replace the circuit board.
After finding cause of overheating,
No
replace the thermal fuse.
Inspect the usage status of the unit.
• If error display 99, then end of service life: replace
the unit.
• If error display 90
• Inspect burner specification
(Inspect gas type, nozzle, secondary pressure)
• Inspect vent passageways for blockage, etc.
Yes Replace the circuit board.
Check the water flow sensor.
• Check using maintenance information monitor no. 15.
Test when hot-water supply valve is fully opened
and 1.7L/min or more is displayed.
(1) Open the hot-water supply valve and measure
the voltage between Yellow 2 (+) and Blue
7 (-) of connector 75 on the circuit board.
DC 0.5 - 15V
Normal
Yes Continue to "3. Water inlet...".
No Continue to (2).
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