Troubleshooting - White Rodgers 50M56U-751 Installation Instructions Manual

TROUBLESHOOTING

Red LED
Flash Error/Condition
1 External lockout (exceeded retries)
2 Pressure switch stuck closed
3 Pressure switch stuck open
4 Open high temperature limit switch or open
rollout switch
5 Flame sensed with gas valve de-energized
or open rollout switch
6 Open circuit between pin 5 and 11
7 Low flame sense current
8 Ignitor relay fault
Rapid Flash Reversed polarity
Continuous Normal operation
On
Off Control failure
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Comments/Troubleshooting
Failure to sense flame is often caused by carbon deposits on
the flame sensor, a disconnected or shorted flame sensor lead
or a poorly grounded furnace. Carbon deposits can be cleaned
with emery cloth. Verify sensor is not contacting the burner
and is located in a good position to sense flame. Check sensor
lead for shorting and verify furnace is grounded properly. Verify
gas supply to valve, gas valve in "On" position and appliance
lighting properly. Verify flame reaches flame sensor during
ignition attempts and gas pressures are correct.
Pressure switch stuck closed. Check switch function, verify
inducer is turning off. Refer to wiring diagram, terminals PSI /
PSO.
Check pressure switch function and tubing. Verify inducer is
turning on and pulling sufficient vacuum to engage switch.
Refer to wiring diagram, terminals PSI / PSO. Also check low
inlet gas pressure (if used).
Verify continuity through limit switch circuit. Refer to wiring
diagram terminals, HLI / HLO or check open rollout switch.
Verify the gas valve is operating and shutting down properly.
Flame in burner assembly should extinguish promptly at the
end of the cycle. Check orifices and gas pressure.
Verify continuity through in 5 and 11.
Low flame sense current is often caused by carbon deposits on
the flame sensor, a poorly grounded furnace or a mis-aligned
flame sense probe. Carbon deposits can be cleaned with
emery cloth. Check or improve furnace and module ground.
Verify sensor is located in or very near flame as specified
by the appliance manufacturer. Refer to wiring diagram FS
terminal and GND.
This flash code does not indicate a broken, disconnected or
shorted ignitor. It indicates the ignitor relay contacts on the
ignition module are not functioning properly. Replace the
ignition module.
Verify the control and furnace are properly grounded. Check
and reverse polarity (primary or secondary) if incorrect.
No fault
Verify power to the control, replace control if power is at the
control and no lit Red LED