Fan Mode; Troubleshooting - Emerson White-Rodgers 21M51U-843 Installation Instructions Manual

FAN MODE

Output
Thermostat - G
Blower (Lo Heat Speed)
EAC
LED
Green Amber Red
LED LED LED
Flash Flash Flash
1
2
3
4
5
6
7
8
9
10
11
12
Solid
Fan until Thermostat is Satisfied
2 sec
Green LED – 1 Flash
Error/Condition
Flame sensed when no flame
should be present
Pressure switch stuck closed/
inducer error
1st-stage pressure switch stuck
open/inducer error
Open limit switch
Open rollout/open fuse detect
1st-stage pressure switch cycle
lockout
External lockout (retries)
External lockout (ignition recycles
exceeded where flame is
established and then lost)
Grounding or Reversed polarity
Control valve contacts energized
with no call for heat
Limit switch open – possible
blower failure overheating limit
Ignitor contact failure
Internal fault condition

TROUBLESHOOTING

Comments/Troubleshooting
Verify the gas valve is operating and shutting down properly.
Flame in burner assemble should extinguish promptly at the
end of the cycle. Check orifices and gas pressure.
Pressure switch stuck closed. Check switch function, verify
inducer is turning off.
Check pressure switch function and tubing. Verify inducer is
turning on the pulling sufficient vacuum to engage switch.
Verify continuity through rollout switch circuit.
Verify continuity through rollout switch circuit, check fuse.
If the first stage pressure switch cycles 5 times (open,
closed) during one call for heat from the thermostat the
control will lockout. Check pressure switch for fluttering,
inconsistent closure or poor vacuum pressure.
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.
Check items for exceeded retries listed above and verify
valve is not dropping out allowing flame to be established
and then lost.
Verify the control and furnace are properly grounded. Check
and reverse polarity (primary) if incorrect.
Verify valve is not receiving voltage from a short. If a valve
wiring is correct and condition persists, replace control.
Possible blower failure, restricted air flow through appliance
or duct work. Verify continuity through limit switch circuit and
correct overheating cause.
Fault code indicates the control ignitor contacts are not
functioning properly. Replace control.
Control contacts for gas valve not operating or processor
fault. Reset control. If condition persists replace control.
OPERATION
5