UENR0623-02 87 Electrical System Electrical System c. The value of the voltage is less than the voltage in step 1.b. Go to step 6. Note: Severely discharged batteries can cause low system voltage. This can occur even while the engine is running above idle, and the alternator is working properly. Correct low engine idle is important. All alternators that are installed on this engine are self-excited. The alternators must exceed the turn on speed before charging will begin. i03635721 Alternator - Test Inspect the alternator for any visible faults. The faults could be the following items. 3. Ensure that the batteries are not fully charged. Frayed wires or damaged wires a.
Fully charged batteries have open circuit voltage above 12.5 V on 12 V systems or 25 V on 24 V systems. Loose connections or damaged connections Loose alternator pulley b. If the batteries are fully charged then crank the engine for 30 seconds. This reduces the battery voltage. Loose alternator or damaged alternator 1. Put the positive lead + of a suitable multimeter on the B+ terminal of the alternator. Put the negative - lead on the ground terminal or on the frame of the alternator. Put a suitable ammeter around the positive output wire of the alternator. c. Connect a current probe or an ammeter to a digital multimeter. The multimeter must have a peak hold feature.
Ensure that the probe is zeroed. Clamp the probe around the output wire B+ . a. Turn the keyswitch to the ON position but do not start the engine. d. Set the multimeter to peak hold or max mode . b. The system voltage matches the specification. Go to step 2. e. Turn on all electrical accessories. c. The system voltage is less than the specification. Check if the battery is in good condition. Refer to Systems Operation, Testing and Adjusting, “Battery - Test” for the correct procedure. Go to step 5.a if the battery is in good condition. f. Start the engine and run the engine at least 75% of full throttle. The peak current will appear on the multimeter. g.
The current is at least 90% of the peak output of the alternator. Go to step 4 or step 5. 2. Put the positive lead + of a suitable multimeter on the B+ terminal of the alternator. Put the negative - lead on the ground terminal or on the frame of the alternator. h. The current is less than 90% of the peak alternator output. Go to step 6. Note: This test procedure is for applications with a main disconnect switch. a. Start the engine and run the engine at least 75% of full throttle. Record the voltage on the multimeter. 4. Turn off all accessories. Turn the keyswitch to the OFF position. b. The voltage should be higher than the voltage in step 1.b.
The voltage is less than the maximum voltage listed for the alternator. The alternator is partially charging. Go to step 3. The voltage is more than the maximum voltage listed for the alternator. There is overcharging of the alternator. Check the alternator wiring. Refer to Systems Operation, Testing and Adjusting, “Charging System - Test” for the correct procedure. a. Connect a current probe or an ammeter to a digital multimeter. Ensure that the probe is zeroed. Clamp the current probe or an ammeter around the ground cable. Clamp the tool with the positive side away from the battery. Record the value of the electrical current. b. The current value is below 2 amperes. Go to step 4.d. c.
The current value is above 2 amperes. Go to step 7.