How to Disconnect a Battery to Troubleshoot an Alternator

Disconnect the battery with caution.

Disconnecting your car's battery may appear to be a simple task, but safety is paramount when dealing with any electrical component. The battery is responsible for powering all the components of the car that require a 12 volt current to operate. If the car's battery is disconnected improperly it can short-circuit your entire electrical system, even cause death from electrocution. Disconnecting the battery to troubleshoot your alternator can safely be done at home. However you should always use care and caution while performing this task yourself.

Things You'll Need

• Socket wrench set
• Black electrical tape
• White painter's tape
• Empty 5 gallon bucket

Instructions

1. Use your socket wrench to completely loosen and remove the negative terminal lead. The car battery's negative terminal will have a minus symbol next to it on the top of the battery.

2. Pop the battery cable out of the plastic trim clip holding it flat against the car battery.

3. Wrap the entire metal end of the battery cable with black electrical tape. Two layers of the tape will be sufficient.

4. Write the word "negative" on a small portion of the painter's tape and place it on the negative battery cable.

5. Loosen and remove the positive battery cable, and also pop it out of the plastic trim clip. Wrap the metal end of the cable with black tape, and mark it with painter's tape so it reads "positive." Lay the battery cables opposite of each other.

6. Unbolt the two j-bolt nuts holding the battery to its tray. If your car battery doesn't have j-bolts, the two nuts you have to remove are at the base of the battery on either side. Place the bolts and nuts together aside near your work area.

7. Set the empty bucket near the front end of the car, so the bottom is facing up. Slowly and carefully with both hands, lift the car battery from its tray. Place the battery down on the bucket gently.

8. Unplug the wiring harness connected to your alternator. Remove the positive cable from the alternator and tape the metal end with black tape. The power cables bolt will be under the black rubber cap on the alternator. Troubleshoot the alternator, then reverse this process exactly to reinstall and connect your car battery.

Tips & Warnings

• Always reconnect the "negative" battery cable to its terminal last to avoid short circuiting your car's electrical system.

References

• "Road & Track Illustrated Automotive Dictionary"; John Dinkel; 2000
• "How to Diagnose and Repair Automotive Electrical Systems"; Tracy Martin; 2005
• "Auto Repair For Dummies"; Deanna Sclar; 1999