SEAL-OIL 4N7527 - Caterpillar

Often when problems with the charging system are being investigated, the alternator is not the problem. If a low battery condition is present test the batteries first. See Special Instruction, SEHS7633, "Battery Test Procedure" for more information. If the engine cranks slowly, then test the starting system. See Service Magazine, SEPD0020, "Testing The Starter On The Engine" for more information. If a warning indicator for the charging system is ON, see Service Magazine, SEBD1751, "Difference Between Alternator Indicator In Electronic Monitoring System (EMS) And Low Voltage Indicator In Operating Monitoring System (OMS)". When a problem with the charging system is suspected, then complete the testing that is outlined in this Special Instruction. See "Initial Troubleshooting Procedure" in order to begin troubleshooting. The procedures in this Special Instruction are designed to guide you to the problem with as little testing as possible. In most cases, you will only use a few of the tests to diagnose a problem. Initial Troubleshooting Procedure
CHECK THE RESISTANCE OF THE EXCITATION CIRCUIT (Check 1). This step is only for alternators with external excitation when the terminal for excitation is labeled: "1", "REG" and "D+". See "Alternator Specifications" if the method of excitation is unknown. Go to Step 3 if your alternator is self-excited. Go to Step 2 if your alternators excitation terminal is labeled with "IG".
If the generator set is equipped with a disconnect switch, turn the disconnect switch to the ON position.
Verify voltage at the excitation terminal. Connect the red lead from a multimeter to the excitation terminal. Connect the black lead to a ground source. The ground source is the alternator case ground.
Read the voltage that is shown on the multimeter.Expected Result - The voltage reads at least 0.2 V.Results -
OK: The voltage reads 0.2 V or more. The excitation circuit is correct. Proceed to Step 3.
NOT OK: The voltage is less than 0.2 V. There is a fault in the wiring harness to the alternator or there is a poor electrical connection. Correct the problem. Watch for a recurrence of the problem.
CHECK THE RESISTANCE OF EXCITATION CIRCUIT (Check 2). This step is only for alternators with external excitation when the terminal for excitation is labeled: "IG". See "Alternator Specifications" if the method of excitation is unknown. Go to Step 3 if your alternator is self-excited.
Turn the disconnect switch to the ON position.
Verify voltage at the excitation terminal. Connect the red lead from a multimeter to the excitation terminal. Connect the black lead to a ground source (alternator case).
Read the voltage that is shown on the multimeter.Expected Result - The voltage is within 0.5 V of the battery voltage.Results -
OK: The voltage reads battery voltage. The excitation circuit is correct. Proceed to Step 3.
NOT OK: The voltage is below battery voltage by more than 0.5 DCV. There is a fault in the wiring harness to the alternator or there is a poor electrical connection. Correct the problem. Watch for a recurrence of the problem.
CHECK THE SYSTEM VOLTAGE.
Before starting the generator