Micro 420 Electrical System Tester

Fig 1: Micro 420 Electrical System Tester

Courtesy of CHRYSLER LLC

The Micro 420 automotive battery tester is designed to help dealership technicians diagnose a defective battery. Follow the instruction manual supplied with the tester to properly diagnose a vehicle. If the instruction manual is not available, refer to STANDARD PROCEDURE , which includes the directions for using the Micro 420 electrical system tester.

CONDITION	POSSIBLE CAUSES	CORRECTION
THE BATTERY SEEMS WEAK OR DEAD WHEN ATTEMPTING TO START THE ENGINE.	1. The electrical system ignition-off draw is excessive.	1. Refer to BATTERY IGNITION-OFF DRAW TEST PROCEDURE for the proper test procedures. Repair the excessive ignition-off draw as required.
	2. The charging system is faulty.	2. Determine if the charging system is performing to specifications. Refer to CHARGING SYSTEM article for additional charging system diagnosis and testing procedures. Repair the faulty charging system as required.
	3. The battery is discharged.	3. Determine the battery state-of-charge using the Micro 420 battery tester. Refer to STANDARD PROCEDURE for additional test procedures. Charge the faulty battery as required.
	4. The battery terminal connections are loose or corroded.	4. Refer to CABLES for the proper battery cable diagnosis and testing procedures. Clean and tighten the battery terminal connections as required.
	5. The battery has an incorrect size or rating for this vehicle.	5. Refer to SPECIFICATIONS for the proper size and rating. Replace an incorrect battery as required.
	6. The battery is faulty.	6. Determine the battery cranking capacity using the Micro 420 battery tester. Refer to STANDARD PROCEDURE for additional test procedures. Replace the faulty battery as required.
	7. The starting system is faulty.	7. Determine if the starting system is performing to specifications. Refer to STARTING SYSTEM article for the proper starting system diagnosis and testing procedures. Repair the faulty starting system as required.
	8. The battery is physically damaged.	8. Inspect the battery for loose terminal posts or a cracked and leaking case. Replace the damaged battery as required.
THE BATTERY STATE OF CHARGE CANNOT BE MAINTAINED.	1. The battery has an incorrect size or rating for this vehicle.	1. Refer to SPECIFICATIONS for the proper specifications. Replace an incorrect battery as required.
	2. The battery terminal connections are loose or corroded.	2. Refer to CABLES for the proper cable diagnosis and testing procedures. Clean and tighten the battery terminal connections as required.
	3. The electrical system ignition-off draw is excessive.	3. Refer to BATTERY IGNITION-OFF DRAW TEST PROCEDURE for the proper test procedures. Repair the faulty electrical system as required.
	4. The battery is faulty.	4. Test the battery using the Micro 420 battery tester. Refer to STANDARD PROCEDURE for additional test procedures. Replace the faulty battery as required.
	5. The starting system is faulty.	5. Determine if the starting system is performing to specifications. Refer to STARTING SYSTEM article for the proper starting system diagnosis and testing procedures. Repair the faulty starting system as required.
	6. The charging system is faulty.	6. Determine if the charging system is performing to specifications using the Micro 420 battery. Refer to CHARGING SYSTEM article for additional charging system diagnosis and testing procedures. Repair the faulty charging system as required.
	7. Electrical loads exceed the output of the charging system.	7. Inspect the vehicle for aftermarket electrical equipment which might cause excessive electrical loads.
	8. Slow driving or prolonged idling with high-amperage draw systems in use.	8. Advise the vehicle operator as required.
THE BATTERY WILL NOT ACCEPT A CHARGE.	1. The battery is faulty.	1. Test the battery using the Micro 420 battery tester. Charge or replace the faulty battery as required.