White Rodgers 50M56U-843 Thermostat User Manual


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www.white-rodgers.com
www.emersonclimate.com
White-Rodgers is a division
of Emerson Electric Co.
The Emerson logo is a
trademark and service mark
of Emerson Electric Co.
Red LED
Flash Error/Condition Comments/Troubleshooting
1 Externallockout(exceededretries) 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amereachesamesensorduring
ignition attempts and gas pressures are correct.
2 Pressure switch stuck closed Pressure switch stuck closed. Check switch function, verify
inducer is turning off. Refer to wiring diagram, terminals PSI /
PSO.
3 Pressure switch stuck open 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.
4 Open high temperature limit switch Verifycontinuitythroughlimitswitchcircuit.Refertowiring
diagram terminals, HLI / HLO.
5 Flame sensed with gas valve de-energized 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.
6 Open rollout switch Verifycontinuitythroughrolloutswitchcircuit.Refertowiring
diagram terminals, RO IN / RO OUT.
7 Low flame sense current 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ameasspecied
by the appliance manufacturer. Refer to wiring diagram FS
terminalandGND.
8 Ignitor relay fault 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.
Rapid Flash Reversed polarity Verifythecontrolandfurnaceareproperlygrounded.Check
and reverse polarity (primary or secondary) if incorrect.
Continuous
On
Normal operation No fault
Off Control failure Verifypowertothecontrol,replacecontrolifpowerisatthe
controlandnolitRedLED
TROUBLESHOOTING
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