105407-5721 ZEXEL 9 420 610 719 BOSCH GOVERNOR 9420610719 1054075721

Fig. 5-Output TerminalStart engine and run at approximately 1500 rpm. Connect voltmeter negative lead to alternator ground terminal and connect positive lead to alternator auxiliary terminal (Fig. 4). Voltmeter should read 15.4 volts. Now move voltmeter positive lead to alternator output terminal (Fig. 5). Voltage reading should be 14.4 volts.If voltage at auxiliary terminal is 15.4 volts, while at the output terminal it is 12 volts or battery voltage, the isolation diode is open. Replace it. Test No. 4 - Field Draw Test (Key Switch Off)Detach regulator and let hang by red and black wires. DO NOT allow regulator to touch the output terminal. If test ammeter is not equipped with a 1/4-ohm resistor, a 1/4-ohm resistor should be connected in series with the ammeter to protect the meter.
Fig. 6-Field Terminal - Test 4Disconnect green field wire from field terminal. Connect ammeter from output terminal (2, Fig. 6) to field terminal (1). Current reading should be 2 to 2.5 amps. If less than this, check brushes and slip rings. Test No. 5 - Checking Alternator and Regulator With Regulator Disconnected (Key Switch On - Engine Running)Disconnect the regulator from the connector. Disconnect the green wire from the field terminal. Connect a jumper wire from the output terminal (2, Fig. 6) to the field terminal (1). Connect voltmeter negative lead to ground terminal and connect voltmeter positive lead to regulator terminal (3).Start engine and run at slow idle. This test isolates the defect to either the alternator or regulator.If voltage at regulator terminal rises to 15-16 volts now, when it did not with regulator connected in Test No. 3, then the regulator is defective and should be replaced.If voltage does not rise at regulator terminal and the field circuit was okay in Test No. 4, then the stator or rectifier diodes are defective. See Section 16, Group 1672 for testing diodes and stator. Test No. 6 - Alternator OutputIf not using JDST-23 tong-type ammeter, disconnect wire from alternator output terminal and connect ammeter from alternator output terminal 2, Fig. 6 to starter solenoid "Bat" terminal. Connect voltmeter negative lead to ground and connect positive lead to output terminal (2, Fig. 6). Connect a carbon pile resistor (turned off) to the battery.Run engine at approximately 1400 rpm. Use a master tachometer to measure rpm. Adjust carbon pile to obtain maximum alternator output at 13 to 15 volts. Ammeter should read 25 amps or more for the 35 amp alternator and 43 amps for the 55 amp alternator. Test No. 7 - Testing RegulatorThe regulator must be checked with an alternator that is in good condition. If the alternator is questionable, check it as previously instructed.Connect voltmeter with 0.1 volt accuracy to the alternator output terminal and ground terminal (Fig. 5). With charged batteries and the regulator brought to operating temperature (fifteen minutes operation), the voltage should be as specified for the surrounding air temperature. See chart below. If battery is partially discharged, it may be necessary to connect a