Caterpillar 3412C Generator Set

Tools: crane, dial indicator, shims, torque wrench

1. Loosen all bolts connecting base to foundation; loosen all bolts fastening engine supports and generator supports to base.
2. Ensure enough clearance between bolts and bolt holes in base, engine supports, generator supports at all locations.
3. Check clearance between base and foundation at all mounting locations; use shims to prevent deflection; tighten base-to-foundation bolts to final torque.
4. While generator supported by crane, loosen all bolts (2) fastening generator to flywheel housing; tighten alternate bolts to final torque; check clearance between base and engine and generator support
5. Tighten all bolts fastening engine supports and generator supports to base to half of final torque; loosen all bolts (2); measure gap between generator and flywheel housing; ensure bolts centered in c
6. Gaps at (E), (F), (G), (H) should be more than 0.03 mm (0.001 inch) and less than 0.13 mm (0.005 inch); adjust shims or move rear of generator right or left.
7. After shim correction, tighten generator support bolts to half of final torque 450 N-m (332 Ib ft); check gaps; repeat until 0.13 mm (0.005 inch) or less; begin with Step 5.
8. Install dial indicator on base with tip next to support mounting bolt (4); put tip on support (3); check while tightening bolt to final torque; if indicator moves more than 0.13 mm (0.005 inch), insta

Tools: shims, torque wrench

1. Loosen all bolts connecting base to foundation; loosen all bolts fastening generator supports and engine supports to base.
2. Ensure clearance between bolts and bolt holes in base, engine supports, generator supports at all locations.
3. Check clearance between base and foundation at all mounting locations; use shims to prevent base deflection; tighten base-to-foundation bolts to final torque.
4. Check clearance between base and engine, base and engine supports, base and generator supports over entire length; use shims to prevent support deflection; tighten all mounting bolts to final torque.

⚠ Replace belts for multiple groove pulleys in matched sets.

Tools: Belt tension gauge (110 N / 25 lb force)

1. Remove the belt guard.
2. Loosen mounting bolt (2) and adjusting nuts (1).
3. Turn adjusting nuts to increase or decrease belt tension.
4. Check deflection is 13 to 19 mm with 110 N applied midway.
5. Tighten the adjusting nuts; tighten the mounting bolt.
6. Reinstall the belt guard.
7. Check adjustment again after 30 minutes at rated rpm if new belts.

⚠ Replace multiple drive belts in matched sets

1. Check belt tension between the first 20 to 40 hours.
2. Apply 110 N (25 lb) of force midway between pulleys.
3. Belt should deflect 13 to 19 mm (0.50 to 0.75 inch).
4. Loosen mounting bolts and the adjusting bolt.
5. Move the alternator to increase or decrease belt tension.
6. Tighten adjusting bolt; tighten mounting bolts.
7. Check tension again after 20 hours if new belts installed.

⚠ Hot engine components can cause burns.

⚠ Only qualified service personnel should perform this maintenance.

1. Ensure the engine cannot be started; do not use the starting motor to turn the flywheel.
2. Ensure the engine is stopped and allow valves to cool.
3. Refer to the Systems Operation/Testing and Adjusting Manual for the complete procedure.
4. Set inlet valve lash to 0.38 mm (0.0150 inch).
5. Set exhaust valve lash to 0.76 mm (0.030 inch).
6. Perform initial adjustment at the first scheduled oil change.

Tools: torque wrench, shims

1. Loosen the sixteen close coupled adapter bolts (2); visually ensure they are centered in clearance holes.
2. Check gaps at 3, 6, 9, and 12 o'clock positions; use 2, 4, 8, and 10 o'clock if 12 and 6 are inaccessible.
3. If gaps are between 0.03 mm (0.001 inch) and 0.13 mm (0.005 inch), tighten all bolts; alignment check complete. If not, loosen bolts fastening generator to base frame; adjust shims; move rear of gener
4. After adjustment, tighten generator mounting bolts to one half of standard torque 450 N-m (332 lb ft); repeat procedure starting with Step 1.

⚠ The VR3 regulator is protected by a fuse(s) and a solid-state overcurrent protection. If a fuse becomes open, contact a Caterpillar dealer.

1. Remove the access panel of the generator.
2. Loosen the locknut on the voltage droop potentiometer (1).
3. Remove the protective screw from the voltage level potentiometer (2) and from the voltage gain potentiometer (3).
4. Turn the voltage droop potentiometer (1) counterclockwise to zero droop. Tighten the locknut.
5. Turn the voltage gain potentiometer (3) counterclockwise to zero, then to about 1/4 of full range of clockwise travel.
6. Perform required maintenance on the engine before you start the engine.
7. Start the engine and allow the engine to warm up.
8. Increase engine speed to full governed rated speed (high idle).
9. Set the no-load voltage with the voltage level potentiometer (2) or the voltage adjust rheostat.
10. Close the load circuit breaker and apply full load gradually. Adjust governor control to nameplate frequency or rated speed.
11. If the voltmeter reading increases above no-load voltage, turn the voltage gain potentiometer counterclockwise. If it decreases, turn it clockwise.
12. Remove the load. If necessary, adjust the voltage level potentiometer (2) to obtain desired voltage.
13. Apply the load. Repeat Steps 10 through 12 until the voltage at no load equals the voltage at full load.
14. Tighten the locknuts. Install the protective screws and the access panel of the generator.

⚠ Do not operate the generator set at a speed higher than one-half of the rated speed.

Tools: 6V-7070 Digital Multimeter, 12 VDC battery, Potential Transformer

1. Stop the generator. Connect the potential transformer's high voltage winding to generator terminals T1 and T2. Connect the voltmeter to the low voltage winding.
2. Disconnect wires F1+ and F2- from the voltage regulator. Disconnect the generator from the load.
3. Connect a 12 VDC automotive battery to wires F1+ and F2-.
4. Operate the generator set at half the rated speed.
5. Measure the AC voltage across the low voltage terminals corresponding to T1-T2, T2-T3, and T3-T1. Record the voltages.
6. Monitor the voltage between any two locations, then decrease the generator set speed by 10 percent and increase it by 10 percent.
7. The measured voltages should be nearly equal and should measure a minimum of 85 VAC.
8. When speed is decreased by 10 percent the voltages should decrease by 10 percent; when increased by 10 percent the voltages should increase by 10 percent.

⚠ Dangerous voltages are present at the generator

Tools: 6V-7070 Digital Multimeter, 9U-7330 Multimeter, 146-4080 Digital Multimeter, 7X-1710 Multimeter Probe Group

1. Remove the cover from the exciter.
2. Remove the nut that secures the rectifier to the heat sink.
3. Remove the diode lead.
4. Lift the rectifier from the heat sink.
5. Connect ohmmeter leads across the rectifier; note the reading.
6. Reverse the ohmmeter leads; note the reading.
7. Replace rectifier if low resistance in both directions or high in both.

Tools: 6V-7070 Digital Multimeter, 9U-7330 Multimeter, 146-4080 Digital Multimeter (RS-232), 7X-1710 Multimeter Probe Group

1. Remove the cover from the exciter.
2. Remove the nut securing the rectifier to the heat sink.
3. Remove the diode lead and lift the rectifier from the heat sink.
4. Connect ohmmeter leads across the rectifier and note reading.
5. Reverse the ohmmeter leads and note reading.
6. Low resistance one direction and high the other indicates a good rectifier.
7. Low resistance both directions indicates shorted rectifier.
8. High resistance both directions indicates open rectifier; replace faulty rectifiers.

Tools: Ohmmeter, Test Light

1. Using an ohmmeter, place the ohmmeter across the varistor. The resistance should be a minimum of 15000 ohms.
2. Disconnect either lead of the varistor (CR7).
3. Place the test light across the varistor.
4. Observe the results. The lamp should not light.
5. Reverse the test light.
6. Observe the results. The lamp should not light.
7. If the test light illuminates in either direction, there is a short in the varistor. Replace any faulty varistors with comparable operating characteristics.

⚠ Damage to engine and generator can result if electric set is operated with a plate assembly that does not have proper clearance.

⚠ If N or O is less than initial A, disassemble and check coupling plate for bowing; replace if bowed.

Tools: dial indicator, straight edge, magnetic bases, crane, torque wrench, 17 5N-4478 Plates

1. Ensure generator is disengaged from engine; clean generator support and base contact surfaces; remove protective material from flywheel pilot bearing bore and coupling contact surface.
2. Remove two engine side covers; rotate engine until no. 1 crankshaft throw is perpendicular; measure crankshaft end play with dial indicator; record as A and divide by two for B.
3. With crankshaft at extreme forward position, measure distance from straight edge to flywheel housing mounting surface (C) and flywheel pilot surface (D); subtract D from C for E.
4. Remove coupling bolts and washers; remove plates, shims, and exhaust fan; lift rotor; locate rotor so air gap equal; move rotor to extreme rear.
5. Place dial indicator on vertical surface of heat sink at rear of rotor shaft; measure rotor end play (approximately 3.81 to 7.62 mm); record F and divide by two for G.
6. Move rotor to extreme rear; position straight edge across mounting ring diameter; measure distance to mounting ring surface (H) and hub mounting surface (I); subtract H from I for J.
7. Bolt a standard set of 17 5N-4478 Plates together; measure thickness in two locations along contour; average as K.
8. Determine number of shims: subtract B, E, G, K from J for L; divide L by 0.8 mm (0.03 inch) for M; round up.
9. Put coupling plate in flywheel bore; check clearance between coupling plate outside diameter and flywheel bore inside diameter.
10. Install coupling plate assembly, bolts (6) and calculated shims; tighten bolts (5) in 180 degree intervals in three stages to 525 + 25 N-m (390 + 20 lb ft).
11. Install guide bolts in flywheel; put generator on engine; install bolts (10); tighten to 100 N-m (75 lb ft) in pairs at 180 degree intervals in three stages.
12. While crane supports generator, place dial indicator on heat sink vertical surface; push generator forward within + 0.50 mm (+ 0.0200 inch) of midpoint of end play.
13. Install fan mounting bolts (11) into flywheel; tighten to 200 N-m (150 Ib ft) in pairs at 180 degree intervals in three stages.
14. Place dial indicators on no. 1 crankshaft throw and heat sink; push crankshaft forward; check crankshaft end play 0.178 to 0.635 mm and heat sink end play 0.076 to 0.635 mm; record N and O.
15. If N or O is less than initial A, disassemble; check coupling plate for bowing; replace if bowed; check calculations; install generator and repeat steps 13 and 15.