Cummins/Onan JWC4-10S-3 — WITH DIAL GAUGE

For the Cummins/Onan JWC4-10S-3.

Applies to: Cummins Onan Jwc4 10S 3

Procedure

1. 4. Assembling Generator to Power Unit.— (1: Reassembly is accomplished by a reversal of the operation used in disassembly. Use care. Make sure that all contact surfaces between parts are clean before fitting together. Tighten all nuts, screws and connections recurely. U'se lockwashers in all places where they were used originally, preferable new lockwashers. (25 After tightening the cup screws which attach * Tun-out should not exceed a total of 010°. To correct ~~ MAINTENANCE—Continued excessive run-out, turn by means of hand crank unul high side is up. Grasp the end of rotor in both hands ‘and push downward, but not too forcibly. Then test again. Kepeat until total run-vut ax shown by dial the cup screws may help to correct excessive run-vut, (3) Be sure to install the rear bearing lock, filling it into the slot in the bearing race. ack the bearing housing 'y full of approved ball-bearing lubricant before instulling cover. Tighten the front engine mounting bults and the huse clamps. Before starting the engine, check your reassembly carefully to make sure no operation has been omitted. h. Testing Windings.— (1) General.. Most of the following testing instructions may be uwd withuul disassembling the generator. In each instance where an exciter arma- ture winding or an alternator field winding tests open-circuited, short-circuited or grounded, the prac- tical repair is to install a new rutor ussembly. If a stator winding tests open-circuited, short-circuited or grounded, the practical repair is to install a new stator winding assembly unless the trouble is in the leads outside the winding proper. The rotor windings and the stator windings can be successfully repaired only by a competent rewinding shop. The tests 1e- quire the use of a 6-volt battery, a 3 or 4 candle- Certain test’ require a d-c volumeter. Before starting the tests, remove the cover Trom the exciter, lift all brushes high in their holders and set the ends of the springs against them so as to hold them high. Then disconnect the four stator winding cables from posts of the a-c terminal block and the large exciter cable from the right hand terminal of the solenoid starting switch. See wiring diagram. Tag the cables 60 as to avoid error in replacing them. In using test prods, make sure that good electrical connec- tion is made at points of contact. (2) Testing Stator Windings for Grounds.— Touch one test prod to the stator frame. Touch the other prod to the terminal of one of the.generator leads. If the lamp lights, the stator winding is grounded. Inspect the cables throughout their lengths, since it is possible that the ground may be in the cable instead of the winding. If so, tape the defective section of the- cable with several layers of half- Tapped rubber tape, then with twa layers of {friction tape. If the ground is in the winding proper, the winding assembly will have to be replaced. « (3) Testing Stator Windings for Open- Circust.--Touch one test prod to the neutral cable terminal. Touch the other test prod to one of the terminal of one of the main stator leads. If the lamp FOR TESTING OPENS & GROUNDS USE 3-4 CANDLE POWER BULB USE 12 VOLT BULB wiITH 2 VOLT BATTERY. USE 6 VOLT BULB wth @® VOU BATTERY. ft does not light, that winding is open-circuited. Repeat the test, sticking the prods through the cable insui- ation and into the copper of the cables near the two terminals instead of touching the terminals. if the circuit does not test open on this test but texts open when contact is made at the terminals, i: indicates that a terminal is loose on its cable. Sweat it on securely with solder. Test between neutral and each of the other stator leads in the same manner. (4) Checking Stator Windings for Short- Circuit.--A short-circuited stator winding will be come excessively heated and soon will destroy the insulation of the short-circuited portions of the wind- ing. This condition may be determined by visual inspection of the stator winding after the alternator frame assembly has been removed from the power unit. A short-circuited stator winding should be replaced with a new one. (5) Testing Alternator Field Winding for Open-Circuit.—Touch one test prod to exch col- lector ring. Mf tne lamp does not light, the field (6) Testing Alternator Field Winding for Short-Cireust.— Hf a considerable number of turns in one coil are short-circuited, that coil will run cooler than other coils which are in yood condition. Grounds a t two points in the winding would short-circuit the intervening portion and the winding would test (7) Testing Rotor Windings for Grounds Touch one test prod to the rotor shalt and the other to a collector ring. If the lamp lights, the alternator field winding is grounded. ‘Touch one test prod to the * 51 MAINTENANCE—Continued tutor shaft and the other to the exciter commutator, If the lamp lights, the exciter armature winding or the commutator is grounded. -3 Testing the Exciter Armature for Open ot Short-Cseeust. - This test may be made by use of an armature growler after first removing the exciter frame. Follow the instructions which acepm- pany the growler. The voltmeter method of testing may be used by one experienced with such testing. iM) Testing Exciter Field Windings for Grounds --Disconnect the shunt field lead near the upper left exciter brush holder and the series field ead near the lower left brush holder. Dis- connect the heavy exciter lead from the right hand terminal of the solenoid starting switch. Touch one test prod to the exciter frame. Touch the other test prod to any of the field leads. If the lamp lights, the winding is grounded. Inspect the leads. If the ground is in a lead, tape the defective section with several layers of half-lapped rubber tape, then with two layers of friction tape. If the ground is in the winding proper, the exciter field must be removed. Then retnove the hollow-head screws which hold the field pole shue to the frame. Remove screws from one pole shoe at a time. push the pole shoe and coil away from the frame and test again for ground. The ground is at the coil last loosened before the test indicates that the ground has been removed. Remove the pole shoe from the coil and locate the grounded spot on the coil by visual inspection. Install a new winding. If a new winding is not available, it may be possible to repair the coil by taping the defective area with several layers of carefully half-lapped friction tape, then shellacing the area. Replace after the shellac has dried. (10) Testing Exciter Field Windings for Open or Short-Circuit.—The exciter field windings are connected in parallel-series and the field assembly must be removed to test for short or open circuits. Disconnect the four coil leads at the point where the shorter, heavy cable connects with the windings. This breaks the connection between the shunt and series windings and provides open ends for testing each winding as a straight series of four coils. Use the test prods to test for open circuit in either winding and for short-circuit between windings. Test for short circuit in the turns of a shunt coil by connect- ing the series of four shunt coils across a 6-volt battery and taking = voltage reading across each coil. If the voltage is lower on one coil than on the others, that coil has some turns short-circuited. Short-circuited turns in one or more series field coils may cause slow cranking or failure to crank at all but would not prevent generating. To test for open cirevit in either the shunt or series field wind- ing, touch one tem prod to each of the twu ends of the series of fuur coils. If the lamp does not light, there is an open circuit. Unless the trouble is located at connections between cuils and easily repaired, install new cuils. (lls Other Tests.—The same test set may be used for many tests for grounds, open circuits or short circuits elsewhere on the power unit. When the lamp lights, obviously the circuit between prods is complete, und vice versa.
2. 51. Suppression Equipment.—

Source: manual:918-0054 Onan JWC4-10S-3 (spec A) Install, Operation, & Maintenance manual.pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.