Cummins/Onan 1400 Generator Set

Tools: DC voltmeter (0-30 range)

1. Remove the end cover and band to allow access to brush rig.
2. Loosen the four cap screws holding the brush rig to the end bell.
3. Mark the new brush rig in the same location as the old one with a reference mark.
4. Make sure the brush rig is free to rotate; rotate the rig back to the original location, start unit and run at rated rpm.
5. Stop unit and inspect brush faces; they must be seated across the thickness of the brush.
6. With a DC voltmeter (0-30 range) attached across the positive and negative brushes, start unit and run at rated rpm and no load.
7. Rotate brush rig in one direction until voltage starts to drop (or sparking occurs); mark this point.
8. Rotate in opposite direction until voltage starts to drop (sparking occurs); mark this point.
9. Approximately halfway between these two marks peak voltage should be reached.
10. Stop unit and tighten all four brush rig cap screws.
11. Start unit again to make sure DC voltage is the same as Step 8 and that no sparking (or arcing) occurs.
12. Mark the ring of the brush rig and end bell with a notch or paint.

Tools: Good battery

1. Connect wires to control as shown for clockwise rotation in Figure 6.
2. Disconnect generator field lead F2 from control box terminal A.
3. Touch this lead momentarily to control box terminal B+, making sure a good battery is used; a definite spark should occur.
4. Reconnect F2 lead to A terminal of control box.
5. Check to see that blower scroll is installed according to clockwise rotation.
6. If changing rotation back from clockwise to counterclockwise, F1 generator lead will be connected to control terminal A; repeat above steps.

⚠ Field must always be polarized with A1 positive or regulator will be damaged.

Tools: 12 volt DC probe

1. Connect generator to control for clockwise rotation (Figure 4).
2. Remove field lead (F1) from terminal #5 of TB1.
3. Apply a positive 12 volt DC probe to terminal #4 of control and touch negative lead momentarily to F1.
4. Be sure F1 is removed from control.
5. Reconnect F1 to terminal #5 and run generator.
6. To change back from clockwise to counterclockwise, F2 will be connected to terminal #5; repeat above steps.

Tools: DC load of at least 75 amperes

1. Run generator at a speed between 1500 and 2500 rpm until warm.
2. Connect a DC load of at least 75 amperes to the battery.
3. Adjust the current adjusting rheostat to give a reading of 55 amperes on the panel ammeter.
4. Reseal to prevent accidental loss of adjustment.

Tools: DC load of at least 75 amperes

1. Run generator at a speed between 1500 and 2500 rpm until warm.
2. Set rheostat to a maximum clockwise position.
3. Connect a DC load of at least 75 amperes to the battery.
4. Turn the current-adjust rheostat to give a reading of 55 amperes on the panel ammeter.

Tools: Accurate DC voltmeter, 60 amp cartridge type fuse

1. Remove the 60 amp cartridge type fuse from the control box.
2. Connect an accurate DC voltmeter across the Al and A2 terminals in the control box with Meter '+' lead to Al and Meter '-' lead to A2.
3. Slowly bring generator up to a speed between 1500 and 2500 rpm observing the voltmeter.
4. If the voltmeter reads backwards check all wiring and repolarize; the reading should be 38 volts.
5. Turn the voltage adjustment rheostat to give a voltmeter reading of 38 volts.
6. Stop the generator, disconnect the voltmeter and reinstall the 60 ampere fuse to its clips.

⚠ Be sure to check for proper polarity before connecting generator field leads to control.

Tools: DC voltmeter (0-10 volts)

1. Connect a DC voltmeter (0-10 volts) across Al positive and A2 negative.
2. Bring generator up to a speed between 1500 and 2500 rpm.
3. Voltage will be very low (less than 1 volt). Al must be positive and A2 negative.
4. If polarity is correct, proceed to connect generator to control.
5. If polarity is backwards, see instructions for flashing the field.

⚠ Do not test for magnetism at just one point of the armature laminations.

Tools: Armature growler (AC), Steel knife blade / hacksaw blade

1. Place the armature in the growler which is connected to alternating current.
2. Hold a steel knife blade (or hacksaw blade) 1/4 inch from the armature laminations.
3. If the steel blade is attracted to any magnetized armature laminations, either the armature windings or commutator is short circuited.
4. Test all of the armature laminations, from one side over to the other side.
5. After testing in one position, revolve the armature about 1/8 revolution and test for magnetism again.
6. Continue revolving and testing until the armature has been tested completely around.

Tools: Ohmmeter and test prods

1. Use an ohmmeter and test prods.
2. Place one test prod on the commutator and the other prod on a bare clean part of the generator frame or armature shaft.
3. The prods must make good electrical contact.
4. If the ohmmeter shows continuity, the armature is grounded.
5. Replace a grounded armature with a new one.

Tools: Armature growler (AC), Smooth steel blade / hacksaw blade

1. Place the armature in the growler which is connected to alternating current.
2. Rub a smooth steel blade (back edge of a hacksaw blade) across the segments of the commutator.
3. A spark should occur as the blade contacts two adjacent segments, indicating the circuit is complete.
4. Rotate the armature just enough to test the next two segments and continue until tested completely around.
5. If no spark occurs, the winding between those two segments is open circuited.

1. Remove only the scroll with screen attached.
2. Turn it end for end and reinstall so scroll is at opposite end of air outlet hole.
3. Arrow printed on the scroll must point in the direction of rotation of the shaft.

⚠ Carefully withdraw the armature to prevent damage to the windings.

Tools: Soft faced mallet

1. Remove the sheet metal end cover; tag or mark each lead as it is disconnected to assure correct reconnection.
2. Remove all brushes and springs.
3. Remove the hex screws holding the end plate at the drive end of the frame.
4. With a soft faced mallet, tap the armature shaft at the brush rig end until the ball bearing is free of the end support.
5. On reassembly, align the bearing notch with its support notch.
6. Carefully withdraw the armature from the frame to prevent damage to the windings.