C3.4B Engines for Caterpillar Built Machines Alternator - Test Caterpillar

Inspect the alternator for any visible faults. The faults could be the following items.

• Frayed wires or damaged wires

• Loose connections or damaged connections

• Loose alternator pulley

• 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.

   1. Turn the keyswitch to the ON position but do not start the engine.

   2. The system voltage matches the specification. Go to step 2.

   3. 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.

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.

   1. Start the engine and run the engine at least 75% of full throttle. Record the voltage on the multimeter.

   2. 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.

   3. 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.

3. Ensure that the batteries are not fully charged.

   1. Fully charged batteries have open circuit voltage above 12.5 V on 12 V systems or 25 V on 24 V systems.

   2. If the batteries are fully charged then crank the engine for 30 seconds. This reduces the battery voltage.

   3. 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+".

   4. Set the multimeter to "peak hold" or "max mode".

   5. Turn on all electrical accessories.

   6. Start the engine and run the engine at least 75% of full throttle. The peak current will appear on the multimeter.

   7. The current is at least 90% of the peak output of the alternator. Go to step 4 or step 5.

   8. 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.

4. Turn off all accessories. Turn the keyswitch to the OFF position.

   1. 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.

   2. The current value is below 2 amperes. Go to step 4.d.

   3. The current value is above 2 amperes. Go to step 7.

   4. Turn the disconnect switch to the ON position. Connect an ammeter across the disconnect switch terminals. Connect the red lead to the terminal on the frame side. Connect the black lead to the terminal on the battery. If a multimeter is used for the test use the ten amp connections to avoid damage.

   5. Turn the disconnect switch to the OFF position. Record the value of the electrical current.

   6. The current is below 0.05 amperes. The charging system is currently good. The fault is possibly an intermittent draw in the system. The batteries may be faulty. Check that no accessories were on during the test.

      Note: The standard acceptable draw is 0.05 amperes. A current that is greater than this value usually indicates a problem. However, some large machines with multiple control modules have a higher acceptable limit.

   7. The current value is above 0.05 amperes. There is a current draw in the system. Go to step 7.

5. Turn off all accessories. Turn the keyswitch to the OFF position.

   1. 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.

   2. The current value is below 2 amperes. Go to step 4.d.

   3. The current value is above 2 amperes. Go to step 7.

   4. Remove the ground cable from the battery terminal. For systems with four batteries or 12 V systems with two batteries, disconnect the ground cables from both negative batteries.

   5. Connect an ammeter between the disconnected battery ground cable and one of the negative battery terminals. Connect the red lead to the cable. Connect the black lead to the terminal on the battery. If a multimeter is used for the test use the ten amp connections to avoid damage.

   6. The current is below 0.05 amperes. The charging system is currently good. The fault is possibly an intermittent draw in the system. The batteries may be faulty. Check that no accessories were on during the test.

      Note: The standard acceptable draw is 0.05 amperes. A current value above this figure usually indicates a problem. However, some large machines with multiple control modules have a higher acceptable limit.

   7. The current value is above 0.05 amperes. There is a current draw in the system. Go to step 7.

6. Check the condition of the poly v-belt and alternator pulley.

   1. If the poly v-belt is oily, clean the pulleys. Replace the poly v-belt. Refer to Disassembly and Assembly, "Alternator Belt - Remove and Install" for the correct procedure. Inspect the poly v-belt for wear or for cracks. Refer to Systems Operation, Testing and Adjusting, "V- Belt - Test". If the poly v-belt is wet, dry the poly v-belt and the pulleys. Retest the system.

   2. Inspect the nut on the alternator pulley. Ensure that the nut is not loose. If the nut is loose, tighten the nut to the correct torque. Refer to Specifications, "Alternator" for the correct torque.

   3. If no faults are found from the procedures in step 6.a and step 6.b, inspect the charging system. Refer to Systems Operation, Testing and Adjusting, "Charging System - Test" for the correct procedure.

7. Turn the keyswitch to the OFF position.

   1. 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 "B+" cable. Clamp the tool with the positive side away from the battery. Record the value of the electrical current.

   2. The current is less than two amperes. Go to step 7.d.

   3. The current is more than two amperes. There is an internal problem with the alternator. Replace the alternator. Refer to Disassembly and Assembly, "Alternator - Remove and Install" for the correct procedure.

   4. Disconnect the wire for "B+" terminal from the alternator. Connect the red lead of the multimeter to the wire for the "B+" terminal. Connect the black lead of the multimeter to the "B+" terminal on the alternator. Set the multimeter to ten amp. Record the value of the electrical current.

   5. The current is below 0.015 amperes. The alternator is operating correctly. There is an electrical load on the machine. Go to step 8.

   6. The current is above 0.015 amperes. There is an internal fault with the alternator. Replace the alternator. Refer to Disassembly and Assembly, "Alternator - Remove and Install" for the correct procedure.

8. Turn off all electrical accessories. Turn the keyswitch to the OFF position.

   1. Connect a current probe or an ammeter to a digital multimeter. Ensure that the probe is zeroed. Clamp the current probe or an ammeter to the main ground cable. Clamp the tool with the positive side away from the battery.

   2. Monitor the current and remove the fuses and circuit breakers one at a time. Check the current after each fuses or each of the circuit breakers are removed. After removing a fuse and checking the current, replace the fuse. Start with the main fuses and proceed to the smaller circuits.

   3. If removing a fuse causes a current drop, then the problem is within that circuit.

   4. Check if any components on the circuit are on.

   5. If all components are switched off, disconnect electrical components on that circuit one at a time and monitor the current.

   6. After all components on the circuit have been disconnected, check the current. If the problem still exists, check the wiring for corrosion. Check if there is a short to ground.

      Note: The standard current is 0.05 amperes. A current value above this figure usually indicates a problem. However, some large machines with multiple control modules have a higher acceptable limit.