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11NO PREVIOUS FAULT - Faults are erased after 48 hrs or whenever power (115V or 24V) is interrupted. Run system through a heating or cooling cycle to recheck system.

12BLOWER ON AFTER POWER UP (115V OR 24V) - Normal operation. Blower will run for 90 sec when furnace power is interrupted during a call for heat and R-W closes.

13LIMIT OR FLAME ROLLOUT SWITCH LOCKOUT - Limit switch was open longer than

3 minutes. Auto-reset will occur after 3 hrs. Flame rollout switch requires manual reset.

See No. 33

14IGNITION LOCKOUT - System failed to ignite gas and prove flame in 4 attempts. Control will auto-reset in 3 hrs.

See No. 34

21GAS HEATING LOCKOUT - Turn off power and wait 5 minutes to retry.

Check for:

•Stuck closed gas valve relay on control.

•Miswire or short to gas valve wire.

22ABNORMAL FLAME PROVING SIGNAL - Flame was sensed while gas valve was de-energized. Inducer will run until fault is cleared.

Check for:

•Stuck open gas valve solenoid or leak.

•Defective control board.

23PRESSURE SWITCH WILL NOT OPEN - Check for:

•Disconnected or obstructed pressure tubing.

•Defective pressure switch.

24LOW-VOLTAGE FUSE IS OPEN - Check for:

•Short in low-voltage wiring including thermostat leads shorting to ductwork or furnace cabinet. Disconnect thermostat leads to isolate short circuit.

31PRESSURE, DRAFT SAFEGUARD (WHEN USED), OR AUXILIARY LIMIT (WHEN USED) SWITCH WILL NOT CLOSE OR REOPEN - If open longer than 5 minutes, inducer shuts off for 15 minutes before retry.

Check for:

•Proper vent sizing or pitch or sag.

•Vent restrictions or high winds.

•Defective inducer motor.

•Low-line voltage (115v).

•Motor start capacitor.

•Low inlet gas pressure.

•Defective pressure switch or connections. If it opens after trial for igniton period, blower will come on for 90 sec recycle delay.

•Inadequate combustion air (for draft safeguard and auxiliary limit switches only).

33LIMIT OR FLAME ROLLOUT SWITCH IS OPEN - If limit switch is open longer than 3 minutes, code changes to No. 13. Check for:

•Blower motor failure.

•Motor start capacitor.

•Open flame rollout switch, manual reset.

•Inadequate combustion air supply (flame rollout switch only).

•Dirty or restrictive filter.

•Restricted duct system.

•Defective limit switch or connections.

•Loose blower wheel.

34IGNITION PROVING FAILURE - If flame is not sensed during the trial for ignition period, the control will repeat the ignition sequence 3 more times before going into lockout, No. 14.

If flame signal is lost after trial for ignition period, blower will come on for 90 sec recycle delay. Check for the following items first before proceding to the next step.

•Gas valve turned off.

•Manual shut-off valve.

•Green wire must be connected to furnace sheet metal.

To determine whether the problem is in the gas valve, igniter, or flame sensor, the system can be operated in the component test mode to check out the ignitor. First, remove the R thermostat connection from the control board and initiate the component test sequence. Does the ignitor glow orange/white hot by the end of the 17 sec warm-up period?

YES

Unplug ignitor harness from control
center and inititate another
component test sequence and check		NO
for 115v between pins 1 and 2 on
the board. Was there 115v present
for the 17 sec period?
	YES

Check for continuity in the harness
and ignitor. Replace defective
component.


Reconnect the R thermostat lead
and set thermostat to call for heat.		NO
Connect voltmeter across gas valve		NO
Connect voltmeter across gas valve
connections. Does gas valve
receive 24v?

	YES
		NO
Does gas valve open and allow gas		NO
to flow?

	YES
		NO
Do main burners ignite?		NO
Do main burners ignite?

	YES
		NO
Do main burners stay on?		NO
Do main burners stay on?

	YES

Allow blower to come on and repeat
test to check for intermittent
operation.

Replace control board.

Check connections. If OK, replace control board.

Check that all gas valves are turned on. Replace valve.

Check for:

•Inadequate flame carryover on rough ignition.

•Low inlet gas pressure.

Repeat call for heat and check flame sensor current during trial for ignition NO period. Is the dc microamperes

below 0.5?

YES

Check connections including equipment ground and retry. Green wire must be connected to furnace sheet metal. If current is near typical value and control will not stay on, replace control board.

Clean flame sensor with fine sandpaper and recheck current. Current is nominally 4.0 to 6.0 microamps DC.

Is current near typical value?			NO
	YES
	YES

		Replace electrode.

			NO
Will main burner ignite and stay on?


	YES

Replace control board.

A98523

Fixed.