andrews Fastflo WHC56 Service Manual page 33

3. Heat exchanger thermistor error.
4. Gas solenoid valve error.
Check the heat exchanger thermistor.
• Check to see if the displayed data of maintenance
information monitor no. 32 and no. 42 match.
(1) Measure the resistance between White 1 and
White 4 of connector Q64.
Temp.(°C)
Normal
Resistance(
Check "4. Gas solenoid..." and
Yes
"6. Bypass flow control...".
Replace the heat exchanger thermistor.
No
Check the gas solenoid valves.
(1) Measure the voltage using connector 10 on the
circuit board.
Normal
Hot water is not discharged.
While presshing the maximum manifold
pressure set button,
SV2 Between Gray 8 - Blue 7 DC80 - 100V
SV3 Between Orange 3 - Blue 7 DC80 - 100V
Warm water is not discharged.
Combust with lowest temperature/lowest flow rate
SV2 Between Gray 8 - Blue 7 DC1V or less.
SV3 Between Orange 3 - Blue 7 DC1V or less.
*For SV2
If combustion cannot be achieved for all burners
with the above values, replace the gas solenoid
valve.
(If combustion is achieved for all burners, check
"5. Gas proportioning...")
NO
– 33 –
0 10 20 30 40 50 60 70 80
kΩ 23.7 15.5 10.3 7.0 4.9 3.5 2.5 1.9 1.4
)
Replace the circuit board.