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Generac 12k Generator Set

The Generac 12k is a 12 kW NG/LP (dual fuel) standby generator set powered by a GT-990 engine. It is available at 120/240 V, 1-phase and 60 Hz. It holds about 1.61 L (0.4 gal) of oil, with a maximum ambient rating of 25 °C. Starting uses group-26 battery rated 525 CCA at 12 V. The set weighs about 199.1 kg (439 lb).

12 kW
Standby
0.992 L
Displacement
1.61 L
Oil capacity
1
Document types

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Specifications

FuelNG/LP (dual fuel)
Frequency60.0 Hz
Standby power12 kW
ControllerLCD digital controller (menu system)
Oil capacity1.61 L
Voltage options120/240 V
Phase1
Circuit breaker50 A
Battery group26R
Battery cranking525 CCA
Battery voltage12 V
Max ambient25 °C
Dry weight199 kg

Engine

GT-990
Oil capacity2.36 L
Displacement0.992 L
Rated speed3600 rpm

Maintenance & consumables

for the GT-990
ItemSpecCapacityPart #Interval
Air filter0C8127 Amazon eBay $28.00 PartsGeek
Fuel filter— find
Oil filterChange with oil070185F200 hr Amazon eBay $14.99 PartsGeek
Belt— find
Coolant—
Oil—200 hr

Common questions

What is the power rating of the Generac 12k?

The Generac 12k is rated 12 kW standby.

What engine does the Generac 12k use?

The Generac 12k is powered by the GT-990 engine.

What fuel does the Generac 12k use?

The Generac 12k runs on NG/LP (dual fuel).

What is the oil capacity of the Generac 12k?

The None GT-990 engine in the Generac 12k has an oil capacity of 2.36 liters.

Troubleshooting

7

Symptoms & remedies

SymptomCauseRemedy
The engine will not crank.1. Fuse blown. 2. Loose, corroded or defective battery cables. 3. Defective starter contactor. (8 kW) 4. Defective starter motor.1. Correct short circuit condition, replace 7.5A fuse in generator control panel. 2. Tighten, clean or replace as necessary. 3. * 4. *
The engine cranks but will not start.1. Out of fuel. 2. Defective fuel solenoid (FS). 3. Open #14 wire from engine control board. 4. Fouled spark plug(s). 5. Valve lash out of adjustment. 6. Choke not operating.1. Replenish fuel/Turn on fuel valve. 2. * 3. * 4. Clean, re-gap or replace plug(s). 5. Reset valve lash. 6. Verify choke plate moves freely.
The engine starts hard and runs rough.1. Air cleaner plugged or damaged. 2. Fouled spark plug(s). 3. Fuel pressure incorrect. 4. Fuel selector in wrong position. 5. Choke remains closed.1. Check, replace air cleaner. 2. Clean, re-gap or replace plug(s). 3. Confirm fuel pressure to regulator is 10-12” water column (0.36-0.43 psi) for LP, and 5-7” water column (0.18-0.25 psi) for natural gas. 4. Move selector to correct position. 5. Verify choke plate moves freely.
The AUTO/OFF/MANUAL switch is set to OFF, but the engine continues to run.1. Defective switch. 2. AUTO/OFF/MANUAL switch wired incorrectly. 3. Defective control board.1. * 2. * 3. *
There is no AC output from the generator.1. Main line circuit breaker is in the OFF (or OPEN) position. 2. Generator internal failure.1. Reset circuit breaker to ON (or CLOSED). 2. *
There is no transfer to standby after utility source failure.1. Defective transfer switch coil. 2. Defective transfer relay. 3. Transfer relay circuit open. 4. Defective control logic board.1. * 2. * 3. * 4. *
Unit consumes large amounts of oil.1. Engine over filled with oil.1. Adjust oil to proper level.

Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.

Parts

57
Part #DescriptionQtySystem
070185Oil Filter1Oil filter Amazon eBay $19.97 PartsGeek
070185FPart # 070185F1Oil filter Amazon eBay $14.99 PartsGeek
0C3008SEAL, 38 I.D. CRANKSHAFT1Seal PartsGeek
0C7065PANEL, ALTERNATOR DIVIDER1Alternator PartsGeek
0C7065APANEL, ALTERNATOR DIVIDER (7KW)1Alternator PartsGeek
0C8127Part # 0C81271Air filter Amazon eBay $28.00 PartsGeek
0E9581Air filter element1Air filter Amazon eBay $21.99 PartsGeek
0G3332Air filter element1Air filter Amazon eBay $15.99 PartsGeek
0G5894Air filter element1Air filter Amazon eBay $19.99 PartsGeek
100-025Air cleaner cover1Air filter PartsGeek
100-030Fuel inlet hose1Hose PartsGeek
RC12YCSpark plug (V-twin GT-999, one per cylinder)2Spark plug Amazon eBay $12.98 PartsGeek
RC14YCSpark plug (single-cylinder GH-410)2Spark plug Amazon eBay $6.77 PartsGeek
021533SET, PISTON RING 90MM2Service part / kit PartsGeek
098290Motor stepper assembly1Service part / kit PartsGeek
098941AGovernor connector housing1Service part / kit PartsGeek
098958AConnector interface assembly1Service part / kit PartsGeek
0A7568Door weldment 1.5EPS2Service part / kit PartsGeek
0C2983SHAFT, GOVERNOR1Service part / kit PartsGeek
0C5372ASSEMBLY, BREATHER1Service part / kit PartsGeek
0C5729ASSEMBLY, CRANKCASE HOUSING WITH SLEEVE1Service part / kit PartsGeek
0C6140ASSEMBLY, ENCLOSURE BASE1Service part / kit PartsGeek
0C6735SUPPORT, ROOF FOLDING2Service part / kit PartsGeek
0C7061ENCLOSURE, FRONT1Service part / kit PartsGeek
0C7062ENCLOSURE, EXHAUST SIDE1Service part / kit PartsGeek
0C7062AENCLOSURE, EXHAUST SIDE (7KW)1Service part / kit PartsGeek
0C7063ENCLOSURE, SIDE & BACK1Service part / kit PartsGeek
0C7063AENCLOSURE, SIDE & BACK (7KW)1Service part / kit PartsGeek
0C7064ENCLOSURE, ROOF1Service part / kit PartsGeek
0C8101APANEL, MUFFLER BOX SIDE1Service part / kit PartsGeek
0C8101BCOVER, MUFFLER BOX1Service part / kit PartsGeek
0C8861PANEL, MUFFLER BOX SIDE (7KW)1Service part / kit PartsGeek
0C8862COVER, MUFFLER BOX (7KW)1Service part / kit PartsGeek
0D1901ASSEMBLY, ENCLOSURE BASE (7KW)1Service part / kit PartsGeek
0D4041ASSEMBLY, CAMSHAFT & GEAR1Service part / kit PartsGeek
0D4042ASSEMBLY, GOVERNOR GEAR1Service part / kit PartsGeek
0D8656Mounting base 1.5L standard & acoustic1Service part / kit PartsGeek
0D8657Radiator support 1.5L Mitsubishi1Service part / kit PartsGeek
0D8660Side brace 1.5L Mitsubishi2Service part / kit PartsGeek
0D8664Duct acoustic & standard compartment 1.5L1Service part / kit PartsGeek
0D8666Roof acoustic & standard compartment 1.5L1Service part / kit PartsGeek
0E1466PIN PISTON2Service part / kit PartsGeek
0E2985PISTON, HC2Service part / kit PartsGeek
0E3372BSEPARATOR, OIL BREATHER3Service part / kit PartsGeek
0E7886ACIRCUIT BREAKER 30A X 2P 240V (7KW)1Service part / kit PartsGeek
0E7886CCIRCUIT BREAKER 40A X 2P 240V (8.5KW)1Service part / kit PartsGeek
0E7886DCIRCUIT BREAKER 45A X 2P 240V (11KW)1Service part / kit PartsGeek
0E7886ECIRCUIT BREAKER 50A X 2P 240V (12KW)1Service part / kit PartsGeek
0E7886GCIRCUIT BREAKER 70A X 2P 240V (15KW)1Service part / kit PartsGeek
0E788912 CIRCUIT LOAD CENTER 125A/240V1Service part / kit PartsGeek
0E7889A8 CIRCUIT LOAD CENTER 125A/240V1Service part / kit PartsGeek
A07360Service ValveService part / kit PartsGeek
A07361Manifold GageService part / kit PartsGeek
A07371Hole Diameter ChartService part / kit PartsGeek
A12434Remote Control (Size 09-24)Service part / kit PartsGeek
A95424Deep Vacuum GraphService part / kit PartsGeek
A95425Triple Evacuation MethodService part / kit PartsGeek

Service, wear & replacement parts referenced for this model and its engine — confirm the exact part for your serial number. See the full parts catalog to search and cross-reference.

Available documents

Owner's manual — 5501-5502-5503-5504-5505-5506-5744 (Generac)Owner's manual — ASPDS-Y-1SG (Generac)

Other sets with this engine

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