Here's a step-by-step procedure for checking the air gap of an alternator
Precautions:
1. Ensure the alternator is turned off and disconnected from power.
2. Wear protective gear (gloves, safety glasses).
3. Consult the alternator's manual or manufacturer's instructions.
Tools needed:

1. Feeler gauge set (0.001-0.050 inches)
2. Straightedge or ruler
3. Flashlight (optional)
Step-by-Step Procedure:
For External Rotor Alternators:
1. Locate the alternator's rotor and stator.
2. Measure the air gap between the rotor and stator using a feeler gauge.
3. Insert the feeler gauge between the rotor and stator, starting from the smallest thickness.
4. Record the measurement (typically 0.010-0.030 inches).
For Internal Rotor Alternators:

1. Remove the alternator's rear cover or access plate.
2. Locate the rotor and stator.
3. Measure the air gap using a feeler gauge.
4. Record the measurement.
Verification:

1. Compare the measured air gap to the manufacturer's recommended specification.
2. Check for any signs of wear, rust, or debris.


Adjustment (if necessary):

1. Consult the manufacturer's instructions for adjustment procedures.
2. Adjust the rotor or stator to achieve the recommended air gap.


Important:

1. Incorrect air gap can affect alternator performance and lifespan.
2. Consult a professional if unsure about the procedure.