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Northern Lights L673 Engine

The Northern Lights L673 is a 0.68 L natural engine rated at 1800 rpm. It powers generator sets from Northern Lights, including the NL673. It holds 2.8 L (0.7 gal) of oil.

Also known as: Lugger L673

Part of the Northern Lights 673 engine family — 4 variants share parts & fitment.

0.676 L

Displacement

1800 rpm

Rated speed

2.8 L

Oil capacity

On this pageSpecs Generator sets FAQ Service intervals Torque & specs Fluids Fault codes Procedures Wiring

Engine specifications

Oil capacity	2.8 L
Displacement	0.676 L
Aspiration	Natural
Rated speed	1800 rpm

Generator sets powered by this engine

Northern Lights NL673

How to read your Northern Lights engine serial & model number →

Common problems

Engine Hard to Start or Will Not Start
Cause: Improper starting procedure
Fix: See starting section of this manual. Take special note of Bypass Switch operation
Lack of Engine Power
Cause: Intake air restriction
Fix: Service air cleaner
Engine Runs Irregularly or Stalls Frequently
Cause: Below normal engine temperature
Fix: Remove and check thermostat
High Fuel Consumption
Cause: Improper type of fuel
Fix: Use correct fuel for temperature.
Engine Overheats
Cause: Low coolant level
Fix: Fill tank or radiator to proper level; Check hoses for loose connections and leaks.
Starter Inoperative
Cause: DC circuit breaker tripped
Fix: If the breaker is tripped, reset it
Starter Cranks Slowly
Cause: Low battery output
Fix: Battery is too small; Battery cables are too small
Engine Emits Black or Gray Exhaust smoke
Cause: Clogged or dirty air cleaner
Fix: Service air cleaner.
Entire Electrical System Does Not Function
Cause: DC circuit breaker tripped
Fix: If breaker is tripped, reset it
Engine Knocks
Cause: Insufficient oil
Fix: Call your dealer.
Engine Emits White Exhaust smoke
Cause: Improper fuel
Fix: Use correct fuel for temperature.
Low Oil Pressure
Cause: Low oil level
Fix: Fill crankcase to proper level.
High Oil Consumption
Cause: Break-in period
Fix: Oil consumption decreases after break in.
Battery Will Not Charge
Cause: Loose or corroded connections
Fix: Clean and tighten battery connections
Below Normal Engine Temperature
Cause: Thermostats not working properly
Fix: Check thermostats.

Compiled from service & troubleshooting documentation across every generator set that uses the Northern Lights L673.

Service intervals

Item	Action	Hours	Months	Notes
Battery electrolyte	Check	50 hr	1 mo	First service — After first 50 hours and every 50 hours; once per month
Cylinder head bolts	Adjust	50 hr		First service — Retighten after first 50 hours when engine is cold
V-belt tension	Check	50 hr		First service — After first 50 hours and every 50 hours
valve clearances	Adjust	50 hr		First service — SP6; after first 50 hours
valves	Adjust	50 hr		First service — After first 50 hours; adjust valves
Battery, cables and terminals	Clean	100 hr
Engine oil and filter (industrial)	Change	100 hr		Every 100 hours industrial only
Radiator fins	Clean	100 hr		Remove debris daily; clean every 100 hours in dusty applications
batteries, cables, terminals	Clean	100 hr		SP18-19; check and clean every 100 hours
Air cleaner	Check	250 hr		Text: inspect every 250 hours; more often in dusty conditions
Engine oil and filter	Change	200 hr		First service — Text also states every 250 hours after the 100-hour change
Engine oil and filter (marine)	Change	200 hr		Every 200 hours marine only
Fuel system	Other	200 hr		Bleed every 200 hours marine only
Primary fuel filter element (Racor)	Change	250 hr		Text: every 250 hours or as necessary
Secondary fuel filter	Change	250 hr		Text: every 250 hours
lube oil filter	Change	200 hr		First service — Every 200 hours
primary fuel filter element	Change	200 hr		Servicing text SP7-9 states change as necessary or every 250 hours.
Battery condition	Test	250 hr		With hydrometer
engine oil	Change	250 hr		First service — SP2; every 250 hours; with oil filter; perform yearly even if hours not reached
lube oil filters	Change	250 hr		First service — SP3; every 250 hours; perform yearly even if hours not reached
radiator filler cap	Check	250 hr		SP16; every 250 hours
Battery state of charge	Test	500 hr		With hydrometer
Injectors	Check	600 hr		Text: injectors checked every 1000 hours
batteries	Test	600 hr		Check state of charge; servicing text SP18-19 states hydrometer check every 250 hours.
cooling system	Clean	500 hr		Check and flush; servicing text SP14 states every 2500 hours or every 12 months, whichever comes first.
cooling system	Other	2500 hr	12 mo	SP14; check and flush every 500 hours per Servicing Schedule Chart
Battery state of charge (hydrometer)	Check	600 hr		Every 600 hours (SP19)
Cooling system	Check	600 hr	12 mo	Check and flush every 600 hours or every 12 months, whichever comes first (SP14)
Impeller in raw water pump (marine)	Change	600 hr		Every 600 hours or as needed (SP17)
Raw water pump impeller (marine)	Change	600 hr
Fuel injection pump	Check	2500 hr		Settings, max speed, idle speed and exhaust smoke checked every 2500 hours
air cleaner element	Replace	1000 hr		Note 6: replace element every 1000 hours.
radiator	Clean	1000 hr		SP16; check and clean radiator every 1000 hours; remove debris daily; clean every 100 hours in very dusty applications
valve clearances	Check	1000 hr		SP6; every 1000 hours or as needed
injection nozzles	Clean	1500 hr		Note 5: clean injection nozzles every 1500 hours.
Heat exchanger (marine)	Clean	2400 hr	12 mo	Once a year or after 2400 hours (SP15)
Cooling system	Drain	2500 hr	12 mo	Flush every 2500 hours or every 12 months, whichever comes first
Generator brushes	Replace	3000 hr		Brush assembly normally replaced within 3,000 hours
Generator bearing	Replace	10000 hr		Replaced by Northern Lights dealer at 10,000 hours
All maintenance	Other		12 mo	Footnote 1: perform all maintenance once a year even if hour level has not been reached

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Service specifications

Type	Item	Value	Unit	Condition
Clearance	Coolant level below filler cap sealing surface	about 1	in. (2.5 cm)	engine cold
Clearance	V-belt deflection at midpoint between fan pulley and alternator pulley	3/16	in.
Gap	V-belt deflection	3/16	in. (5 mm)	midpoint between fan pulley and alternator pulley
Gap	V-belt deflection at midpoint between crankshaft and alternator pulleys	3/16	in. (5 mm)
Other	Cooling water pH level	5.5 to 9.0	pH
Other	Engine oil capacity with new oil filter	3.3 quarts (3.1 liters)	quarts (liters)
Other	Maximum chlorides in cooling water	40	ppm (2.5 grains per gallon)
Other	Maximum dissolved solids in cooling water	340	ppm (20.0 grains per gallon)
Other	Maximum sulfates in cooling water	100	ppm (5.9 grains per gallon)
Other	Maximum total hardness in cooling water	170	ppm (10.0 grains per gallon)
Other	V-belt tension	3/16	in	deflection at midpoint between crankshaft and alternator pulleys
Pressure	Cooling system filler cap release pressure	approximately 7	PSI (0.5 bar)
Pressure	Engine oil pressure (normal reading)	20-60	PSI	after a few seconds of operation
Pressure	Engine oil pressure minimum	above 15	PSI	operating
Pressure	Engine oil pressure normal	20-60	PSI	after a few seconds of operation
Pressure	Minimum oil pressure	above 15	PSI	engine running
Pressure	Normal oil pressure	20-60	PSI	after a few seconds of operation
Pressure	Oil pressure	20-60	PSI	normal reading after a few seconds of operation
Pressure	Oil pressure	above 15	PSI	running
Pressure	Oil pressure normal reading	20-60	PSI	after a few seconds of operation
Pressure	Radiator filler cap pressure valve	7	PSI	approximately
Pressure	Radiator filler cap pressure valve release	7	PSI (0.5 bar)	approximately
Pressure	Radiator filler cap release pressure	approximately 7	PSI (0.5 bar)
Resistance	A-B resistance	0.25	ohm	at 20°C (68°F)
Resistance	AVR J-K resistance	16.6	ohm	at 20°C (68°F)
Resistance	Generator A-B resistance	0.25	ohm	at 20°C (68°F)
Resistance	Generator J-K resistance	16.6	ohm	at 20°C (68°F)
Resistance	Generator U1-V2 resistance	0.56	ohm	at 20°C (68°F)
Resistance	Resistance of A-B	0.25	ohm	at 20°C (68°F)
Resistance	Resistance of J-K	16.6	ohm	at 20°C (68°F)
Resistance	Resistance of U1-V2	0.56	ohm	at 20°C (68°F)
Resistance	U1-V2 resistance	0.56	ohm	at 20°C (68°F)
Temperature	Battery warm before charging frozen battery	at least 16	°C (60°F)	frozen batteries
Temperature	Coolant restart threshold	below 225	°F	after overheating
Temperature	Coolant shutdown threshold	above 230	°F
Temperature	Coolant temperature shutdown point (industrial sets)	230	°F (110°C)	shut off engine immediately if above
Temperature	Coolant temperature to restart (industrial sets)	below 225	°F (107°C)
Temperature	Industrial set normal water temperature (must be below)	225	°F (107°C)
Temperature	Industrial set water temperature shutdown limit	230	°F (110°C)
Temperature	Industrial shutdown temperature	230	°F	shut off immediately if above
Temperature	Industrial water temperature gauge	below 225	°F	operating
Temperature	Marine set normal water temperature (must be below)	200	°F (94°C)
Temperature	Marine set water temperature shutdown limit	205	°F (96°C)
Temperature	Marine shutdown temperature	205	°F	shut off immediately if above
Temperature	Marine water temperature gauge	below 200	°F	operating
Temperature	Maximum ambient temperature	40	°C (104°F)	operation
Temperature	Maximum ambient temperature at generator installation	40	°C (104°F)	during operation
Temperature	Maximum generator operating ambient temperature	40	°C (104°F)	during operation
Temperature	Normal coolant temperature	75 to 90	°C	normal operating
Temperature	Restart temperature after overheat	below 225	°F (107°C)
Temperature	Shutdown overheat temperature	above 230	°F (110°C)	industrial sets
Torque	Cylinder head bolts	26 - 29	ft/lbs	cold; tighten in 2 or 3 passes
Torque	Cylinder head bolts (643 and 673)	26 - 29	ft/lbs (3.5 - 4.0 kg/m)	engine cold
Torque	Fuel injector	43 or 50	ft/lbs
Torque	Fuel return line retaining bolts	22 - 30	ft/lbs
Torque	Injector	43 or 50	ft/lbs	injector installation
Torque	Return line retaining bolts	22 - 30	ft/lbs
Torque	Rocker arm cover nuts	5 - 8	ft/lbs
Torque	Rocker arm cover nuts	7.2 - 8.7	ft/lbs (1.0 - 1.2 kg/m)
Valve clearance	Intake and exhaust valve clearance	0.008	in. (0.2 mm)	cold, engine not running

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Recommended fluids

Fluid	Grade	Standard	Ambient	Capacity	Notes
Coolant	50% water / 50% ethylene glycol antifreeze mix				Recommended as a good year-round coolant; preferred water is distilled, deionized, soft water. Water quality limits: chlorides max 40 ppm/2.5 grains per gallon; sulfates max 100 ppm/5.9; dissolved solids max 340 ppm/20.0; total hardness max 170 ppm/10.0; pH 5.5 to 9.0.
Engine oil	API Service CC/CD/CE single viscosity oils; API Service CC/CD/SF multi-viscosity oils				Use proper weight oil for average operation temperature; never put additives or flushing oil in crankcase
Engine oil	SAE 30 weight Service CC			3.1 L (3.3 quarts)	Use during the first 100 hours; capacity with new oil filter
Engine oil	SAE 5-20W	API Service CC/CD/SF multi-viscosity	below -23°C		Below -10°F (-23°C)
Engine oil	SAE 5W	API Service CC/CD/CE single viscosity	below -23°C		Below -10°F (-23°C)
Engine oil	SAE 5W (single viscosity) / SAE 5-20W (multi-viscosity)	API Service CC/CD/CE (single viscosity); API Service CC/CD/SF (multi-viscosity)	below -23°C		Below -10°F (-23°C); some increase in oil consumption may be expected
Engine oil	SAE 5W / SAE 5-20W	API Service CC/CD/CE single viscosity oils; API Service CC/CD/SF multi-viscosity oils	below -23°C		Below -10°F (-23°C)
Engine oil	SAE 5W single viscosity; SAE 5-20W multi-viscosity	API Service CC/CD/CE or CC/CD/SF	below -23°C		Below -10°F (-23°C)
Engine oil	Service CC 30 weight	API Service CC			Use during the first 100 hours
Engine oil	SAE 10-30W	API Service CC/CD/SF multi-viscosity	-23°C to 0°C		-10 to 32°F (-23 to 0°C)
Engine oil	SAE 10W	API Service CC/CD/CE single viscosity	-23°C to 0°C		-10 to 32°F (-23 to 0°C)
Engine oil	SAE 10W (single viscosity) / SAE 10-30W (multi-viscosity)	API Service CC/CD/CE (single viscosity); API Service CC/CD/SF (multi-viscosity)	-23°C to 0°C		-10 to 32°F (-23 to 0°C)
Engine oil	SAE 10W / SAE 10-30W	API Service CC/CD/CE single viscosity oils; API Service CC/CD/SF multi-viscosity oils	-23°C to 0°C		-10 to 32°F (-23 to 0°C)
Engine oil	SAE 10W single viscosity; SAE 10-30W multi-viscosity	API Service CC/CD/CE or CC/CD/SF	-23°C to 0°C		-10 to 32°F (-23 to 0°C)
Engine oil	SAE 15-40W	API Service CC/CD/SF multi-viscosity	above 0°C		Above 32°F (0°C)
Engine oil	SAE 30W	API Service CC/CD/CE single viscosity	above 0°C		Above 32°F (0°C)
Engine oil	SAE 30W (single viscosity) / SAE 15-40W (multi-viscosity)	API Service CC/CD/CE single viscosity oils; API Service CC/CD/SF multi-viscosity oils	above 0°C	3.1 liters	Above 32°F (0°C); engine capacity with new oil filter is 3.3 quarts (3.1 liters)
Engine oil	SAE 30W single viscosity; SAE 15-40W multi-viscosity	API Service CC/CD/CE or CC/CD/SF	above 0°C	3.0 L	Above 32°F (0°C); capacity with new oil filter
Fuel	ASTM D975; grade no. 2 diesel above freezing 32°F (0°C); grade no. 1 below freezing and for all temperatures above 5,500 ft. (1500 meters)	ASTM D975			Sulfur less than 1% (preferably less than 0.5%); cetane number minimum 45; do not use domestic heating oils, Class B engine, Class D domestic fuels, Class E/F/G/H industrial or marine fuels, ASTM-D975-60T No. 4-D and higher
Fuel	Grade No. 1 diesel	ASTM D975	below 0°C		At ambient temperatures below freezing and for all temperatures at an altitude above 5,500 ft. (1500 meters)
Fuel	Grade No. 2 diesel above freezing 32°F (0°C); Grade No. 1 below freezing and at altitudes above 5,500 ft. (1500 meters)	ASTM D975; sulphur less than 1% (preferably less than 0.5%); cetane number minimum 45			Do not use domestic heating oils, Class B engine, Class D domestic fuels, Class E/F/G/H industrial or marine fuels, ASTM-D975-60T No. 4-D and higher
Fuel	No. 1 diesel	ASTM D975	below 0°C		Below freezing and for all temperatures at altitude above 5,500 ft (1500 meters); sulfur less than 1% (preferably less than 0.5%); cetane number minimum 45
Fuel	No. 2 diesel above freezing 32°F (0°C); No. 1 below freezing and above 5,500 ft	ASTM D975			Sulfur less than 1% (preferably less than 0.5%); cetane minimum 45
Fuel	Grade No. 2 diesel	ASTM D975	above 0°C		At ambient temperatures above freezing 32°F (0°C); sulphur less than 1% (preferably less than 0.5%); cetane minimum 45
Fuel	No. 2 diesel	ASTM D975	above 0°C		Above freezing 32°F (0°C); sulfur less than 1% (preferably less than 0.5%); cetane number minimum 45

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Fault codes

Code	Name	Meaning	Action
04	Actuator drive wire disconnected	Detected when Engine ECU Power ON or Cranking.	Lamp action only when ECU power on; engine does not start during cranking
13	Oil pressure SW failure or wire disconnected	Lamp code 13: Long, Short, Short, Short. Detected when Engine ECU Power ON (EG Start Enable).	Go to Low Power Mode
15	Speed Sensor Failure or wire disconnected	Detected during Cranking or Engine Running.	Engine does not start during cranking; Go to Low Power Mode when running
22	Pressure Sensor failure or wire disconnected	Detected when Engine ECU Power ON (EG Start Enable) or Engine running.	Go to Low Power Mode
33	Pressure Sensor failure or wire disconnected	Detected when Engine ECU Power ON (EG Start Enable) or Engine running.	Go to Low Power Mode

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Procedures

V-Belt Adjustment adjustment

Tools: thumb

Check tension and wear daily.
Press thumb at midpoint between fan pulley and alternator pulley.
Correct tension: belt depresses about 3/16 in. (5 mm).
Loosen alternator tensioning arm bolt and mounting bolt.
Pivot alternator toward engine left or right as required.
Tighten mounting bolt and adjusting bolt.
Recheck tension after tightening.
Recheck after running five minutes at low idle.

V-Belts (SP5) adjustment

Press on the belt at the midpoint between fan pulley and alternator pulley with your thumb.
Tension is correct if the belt can be depressed about 3/16 in. (5 mm).
Loosen the alternator tensioning arm bolt and the alternator mounting bolt.
Pivot the alternator at the mounting bolt toward the engine left or right side as required.
Tighten the mounting bolt and the adjusting bolt.
Recheck belt tension after tightening and again after running 5 minutes at low idle.

Valve Clearance Adjustment adjustment

Adjust after cylinder head bolts are retightened; engine cold and not running.
Turn engine by hand until #1 cylinder inlet valve starts to open and exhaust starts to close.
Turn crankshaft one more full turn and adjust both valves for this cylinder.
Loosen lock nut and adjust clearance between rocker arm and valve guide.
Set clearance to 0.008 in. (0.2 mm) for both intake and exhaust.
Repeat for each cylinder individually.
Replace rocker arm cover and tighten cover nuts to 7.2 - 8.7 ft/lbs.

Valve Clearances adjustment

Adjust valve clearance every 1000 hours, or as needed; engine must be cold and not running.
Turn engine by hand until inlet valve starts to open and exhaust valve starts to close (valves are rocking).
Turn crankshaft one more full turn and adjust clearance on both valves for this cylinder.
Loosen lock nut and adjust clearance between rocker arm and valve guide with adjustment screw.
Set both intake and exhaust valves to 0.008 in. (0.2 mm).
Repeat for each cylinder; adjust each set individually.
Replace rocker arm cover and tighten cover nuts to 5 - 8 ft/lbs (0.8 - 2.3 kg/m).

Valve Clearances (SP6) adjustment

⚠ Valve adjustments should be done after the cylinder head bolts have been re-tightened.

Adjust valve clearance every 1000 hours, or as needed; engine cold and NOT running.
Turn the engine over by hand until the inlet valve starts to open and exhaust starts to close (valves rocking).
Turn the crankshaft one more full turn and adjust the clearance on both valves for this cylinder.
Loosen the lock nut and adjust clearance with the adjustment screw.
Clearance on both intake and exhaust valves is 0.008 in. (0.2 mm).
Repeat for each cylinder; each set of valves must be adjusted individually.
Replace the rocker arm cover; tighten cover nuts to 5 - 8 ft/lbs (0.8 - 2.3 kg/m).

Valve clearance adjustment (SP6) adjustment

Tools: feeler gauge, wrenches

Retighten cylinder head bolts first; engine must be cold and NOT running.
Turn engine by hand until #1 cylinder inlet valve starts to open and exhaust valve starts to close.
Turn the crankshaft one more full turn and adjust both valves for this cylinder.
Loosen the lock nut and adjust clearance between rocker arm and valve guide with the adjustment screw.
Set clearance to 0.008 in. (0.2 mm) on both intake and exhaust valves.
Repeat for each cylinder; each set of valves must be adjusted individually.
Replace rocker arm cover and tighten cover nuts to 7.2 - 8.7 ft/lbs (1.0 - 1.2 kg/m).

Flashing the fields diagnostic

⚠ The AVR must be disconnected when flashing fields or it could be ruined.

Tools: 12 volt DC source, voltmeter

If there is no voltage buildup on startup (zero volts measured), the generator may have no residual magnetic field.
Disconnect the AVR before flashing fields or it could be ruined.
Apply 12 volts DC to terminals K (-) and J (+) as indicated.
Reconnect AVR and check voltage buildup.

Battery Care maintenance

⚠ Battery gas can explode; keep flames and sparks away from batteries.

Tools: hydrometer

Check electrolyte level daily; add distilled water to manufacturer's recommended level.
Check and clean batteries, cables, and cable terminals every 100 hours.
Clean corrosion with water and baking soda solution; flush with clean water.
Tighten terminals and grease them to inhibit corrosion.
Check battery condition with a hydrometer every 250 hours.

Bleeding Fuel System maintenance

⚠ Escaping diesel fuel under pressure can penetrate skin causing serious personal injury.

Tools: cardboard

System is self-bleeding but needs manual bleeding after filter change, running out of fuel, or component removal.
Loosen bleed screw A on top of filter.
Pump hand primer B until pure fuel escapes from screw A, then tighten A.
Loosen bleed screw C; pump hand primer B until pure fuel escapes.
If engine does not start, loosen a fuel line at injector.
Crank engine until pure fuel escapes; tighten connection.
Do each line one at a time.
After starting, check for leaks using cardboard.

Bleeding the Fuel System maintenance

⚠ Escaping diesel fuel under pressure can penetrate skin; relieve pressure before disconnecting lines.

Tools: cardboard

Loosen bleed screw A on top of the filter.
Pump hand primer B on fuel lift pump until pure fuel with no bubbles escapes from bleed screw A; tighten bleed screw A.
Loosen bleed screw C and pump hand primer B until pure fuel escapes.
If engine does not start, loosen a fuel line at the injector and crank until pure fuel escapes; tighten connection.
Do each fuel line one at a time.
After engine starts, check for fuel leaks using cardboard.

Bleeding the fuel system (SP10) maintenance

⚠ Escaping diesel fuel under pressure can penetrate skin causing serious personal injury.

⚠ Use cardboard or wood, not hands, to search for leaks.

Tools: cardboard or wood for leak checking

Loosen bleed screw A on top of the filter.
Pump hand primer B on the fuel lift pump until pure fuel (no bubbles) escapes; tighten bleed screw A.
Loosen bleed screw C and pump hand primer B until pure fuel escapes.
If the engine still does not start, loosen a fuel line at the injector, pump until pure fuel escapes and tighten.
Do each line one at a time.
After starting, use a piece of cardboard to look for fuel leaks.

Break-In Period maintenance

Operate the engine under various conditions, particularly heavy loads with minimal idling.
Constantly check engine temperature and oil pressure.
Change engine oil and filter at 50 hours.
Change oil and filter again at 100 hours.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Voltage reconnection

Voltage	Phase	Connection	Leads	Notes
120		Connect U1 to U2 and V1 to V2 on the output terminal board	120 volt output leads to terminals U1 and V2	Select 120 volt output by connecting control terminal board to 120
120		Connect U1 to U2 and V1 to V2 on the output terminal board; connect 120 volt output leads to terminals U1 and V2.	U1, U2, V1, V2	Control terminal board set to 120. See Figure 20 and Figure 21.
120		Connect the terminals of the control terminal board to 120; connect U1 to U2 and V1 to V2 on the output terminal board; connect 120 volt output leads to terminals U1 and V2	U1, U2, V1, V2	Figure 20 and Figure 21, 120 Volt Output
120	1	Connect V1 and 120 terminals of the control terminal board; connect U1 to U2 and V1 to V2 on the output terminal board; connect 120 volt output leads to terminals U1 and V2	U1, U2, V1, V2	120 Volt Output
120	1	Control terminal board set to 120; output terminal board U1 to U2 and V1 to V2; output leads to U1 and V2	U1, U2, V1, V2	120 volt output
120/240		Connect U2 and V1 on the output board	Output leads to U1 and V2; neutral lead to V1 (or U2)	240 volt output available from leads connected to U1 and V2; divide 120 volt load equally between two 120 volt circuits
120/240		Connect U2 and V1 on the output board; connect output leads to U1 and V2 and neutral lead to V1 (or U2).	U1, U2, V1, V2	240 volt output available from leads connected to U1 and V2. Divide 120 volt load as equally as possible between two 120 volt circuits. See Figure 24 and Figure 25.
120/240		Connect the control terminal board for 240 volts; connect U2 and V1 on the output board; connect output leads to U1 and V2 and neutral lead to V1 (or U2)	U1, U2, V1, V2	240 volt output available from leads connected to U1 and V2; divide the 120 volt load as equally as possible between two 120 volt circuits
120/240	1	Connect the control terminal board for 240 volts; connect U2 and V1 on the output board; connect output leads to U2 and V2 and neutral lead to V1 (or U2)	U1, U2, V1, V2	240 volt output available from leads connected to U1 and V2; 120 volt load should be divided as equally as possible between two 120 volt circuits
120/240	1	Control terminal board set to 240; output terminal board U2 to V1; output leads to U2 and V2; neutral to V1 (or U2); 240 volt output from U1 and V2	U1, U2, V1, V2	Divide 120 volt load as equally as possible between two 120 volt circuits
240		Connect U2 to V1 on the output terminal board		Select 240 volt output by connecting control terminal board to 240
240		Connect U2 to V1 on the output terminal board.	U2, V1	Control terminal board set to 240. See Figure 22 and Figure 23.
240		Connect the terminals of the control terminal board to 240; connect U2 to V1 on the output terminal board	U1, U2, V1, V2	Figure 22 and Figure 23, 240 Volt Output
240	1	Connect V2 to 240 on the control terminal board; connect U2 to V1 on the output terminal board	U1, U2, V1, V2	240 Volt Output
240	1	Control terminal board set to 240; output terminal board U2 to V1	U1, U2, V1, V2	240 volt output

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Parts cataloged across the Northern Lights 673 family

Part #	Description	Category
24-28003	Air Filter Element	Air filter
24-28300	Air Filter	Air filter
22-68000	Kit: new DST-61 regulator with fuse, fuse holder parts and two crimp lugs; includes mounting plate adaptor parts	Avr
22-68035	Kit similar to 22-68000 but does not include the fuse parts	Avr
DST-61	New DST-61 voltage regulator	Avr
M673L2	Platform vibration mounts.	Base
22-68304	Brush assembly	Brush
24-52020	Fuel Filter	Fuel filter
360720020	Fuel Filter Element	Fuel filter
052100280	Gasket (Marine application only, formerly #054109013)	Gasket
165996490	Gasket	Gasket
18-72004	Oil Drain Hose	Hose
18-78009	Hose Assembly 3/8" x 15" (used with oil pan 36-78006)	Hose
140406570	Suction Filter	Oil filter
24-02001	Oil Filter	Oil filter
24-08001	Oil Filter	Oil filter
040109059	Bearing	Service part / kit
040126210	Bearing	Service part / kit
110136445	Intake Valve Seat	Service part / kit
115017630	Piston, standard (includes key #16)	Service part / kit
115104050	Ring Kit, standard	Service part / kit
120026810	Camshaft Assembly (includes keys #2 - 6)	Service part / kit
120166370	Intake Valve	Service part / kit
120456320	Push Rod	Service part / kit
198517103	Bearing, Standard Upper	Service part / kit
198517107	Bearing, undersize 0.25 mm (formerly #198517106)	Service part / kit
198517112	Bearing, Standard Lower	Service part / kit
198517116	Bearing, undersize 0.25 mm (formerly #198517115)	Service part / kit
198517119	Bearing, undersize 0.50 mm (formerly #198517118)	Service part / kit
198517312	Bearing, standard (formerly #198517311)	Service part / kit
198517316	Bearing, undersize 0.25 mm (formerly #198517315)	Service part / kit
198517319	Bearing, undersize 0.50 mm (formerly #198517318)	Service part / kit
198517332	Bearing, Standard Upper (formerly #198517331)	Service part / kit
198517336	Bearing, undersize 0.25 mm (formerly #198517335)	Service part / kit
198517339	Bearing, undersize 0.50 mm (formerly #198517338)	Service part / kit
198517342	Bearing, Standard Lower (formerly #198517341)	Service part / kit
198517346	Bearing, undersize 0.25 mm (formerly #198517345)	Service part / kit
198517349	Bearing, undersize 0.50 mm (formerly #198517348)	Service part / kit
198517630	Bearing, undersize 0.50 mm (formerly #198517109)	Service part / kit
22-48011	Fuse for main circuit (M/NL 673)	Service part / kit
22-68305	Generator bearing	Service part / kit
22-68309	Protective Fuse (for AVR)	Service part / kit
28-68003	Adaptor mounting plate	Service part / kit
38-08015	Northern Lights standard spare parts kit	Service part / kit
38-08019	Northern Lights world class spare parts kit	Service part / kit
052109078	O-ring, Relief Valve	Seal
052109113	O-ring	Seal

Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.

Common questions

What is the oil capacity of the Northern Lights L673?

The Northern Lights L673 engine has an oil capacity of 2.8 liters.

What is the displacement of the Northern Lights L673?

The Northern Lights L673 has a displacement of 0.676 liters.

Which generators use the Northern Lights L673 engine?

The Northern Lights L673 powers 1 generator set(s), including Northern Lights NL673.

What is a common problem with the Northern Lights L673 engine?

A commonly reported issue on generators using the Northern Lights L673 is: Engine Hard to Start or Will Not Start. Cause: Improper starting procedure. Fix: See starting section of this manual. Take special note of Bypass Switch operation.