2nd Ave 7800 Series Inspect the fan make sure there is no blockage of the air

7800 SERIES RELAY MODULES

Table 3. Hold and Fault Message Summary (continued).

Fault Code	System Failure		Recommended Troubleshooting
Fault 18	Flame sensed when shutter is	1.	Check that flame is not present in the combustion chamber.
*Flame Detected*	open and no flame is expected		Correct any errors.
	during PREPURGE.	2.	Make sure that the flame amplifier and flame detector are
			compatible.
		3.	Check the wiring and correct any errors. Make sure F and G
			wires are in individual conduits and protected from stray
			noise pickup.
		4.	Remove the flame amplifier and inspect the connectors.
			Reseat the flame amplifier.
		5.	Reset and sequence the relay module.
		6.	If the code reappears, replace the flame amplifier and/or the
			flame detector.
		7.	If the fault persists, replace the relay module.
Fault 19	Flame was lost during MFEP or	1.	Inspect the main fuel valve(s) and connection(s).
*Main Flame Ign.*	the first 10 seconds of the RUN	2.	Make sure that the fuel pressure is high enough to supply
	state.		fuel to the combustion chamber.
		3.	Make sure the flame detector is positioned to obtain the
			required flame signal strength; reset and recycle.
Fault 20	Low Fire Interlock switch failure	1.	Check wiring and correct any errors.
*Low Fire Sw. Off*	to close during PREPURGE.	2.	Reset and sequence the relay module.
		3.	Use either the manual motor potentiometer to drive the
			motor to the Low Fire position or use the Run/Test Switch
			option, if available. Sequence to Prepurge drive to Low Fire
			and place in the Test position. Adjust the Low Fire Switch
			to make sure that it closes properly.
		4.	Measure the voltage between terminal 18 and G (ground)
			while in the Prepurge drive to Low Fire state. Line supply
			voltage should be present. If not, the switch adjustment is
			incorrect and/or the switch is defective and needs
			replacing.
		5.	Reset and sequence the relay module. If line supply voltage
			was present between the Low Fire Switch and terminal 18,
			and the fault still persists, replace the relay module.
Fault 21	Running Interlock fault during	1.	Check wiring; correct any errors.
*Running ILK*	PREPURGE.	2.	Inspect the fan; make sure there is no blockage of the air
			intake and that it is supplying air.
		3.	Make sure the Interlock Switches are working properly and
			that all switch contacts are free of contaminants.
Fault 22	Lockout Interlock fault during	4.	Reset and sequence the relay module to PREPURGE (place
*Lockout ILK*	PREPURGE.		the Run/Test Switch in the Test position, if available).
			Measure the voltage between terminals 7 and G (ground).
			Line voltage should be present.
Fault 23	Combustion airflow interlock	5.	If steps 1 through 4 are correct and the fault persists,
*Airflow Switch*	fault during PREPURGE.		replace the relay module.
Fault 24	The flame interlock (relay	1.	Check for F leadwire routing. Make sure routing is in its
*Call Service*	module) was on when it should		conduit and isolated from noise-producing circuits.
	be off.
Fault 25	The flame interlock (relay
*Call Service*	module) was off when it should
	be on.
Fault 26	The Manual Open Valve Switch	1.	Check wiring and correct any errors.
*Man-Open Sw. Off*	was off when it should be on	2.	Make sure that the Manual Open Valve Switch is fully open.
	(RM7838B only).	3.	Make sure that the Manual Open Valve Switch is
			functioning properly and that the switch contacts are free
			from contaminants.
		4.	Reset and sequence the relay module.
		5.	Make sure that the Manual Open Valve Switch provides an
			electrical path when closed. Verify that the relay module is
			receiving power at terminal 17.
		6.	If steps 1 through 5 are correct and the fault persists,
			replace the relay module.
			(continued)

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