What is wrong if you replaced the alternator on a 1998 Pontiac Grand Am SE now car will start but then turn itself off?

If your 1998 Pontiac Grand Am SE starts but then immediately shuts off after replacing the alternator, the problem is almost certainly not the alternator itself (unless it's faulty or incorrectly installed). A new alternator should *solve* starting problems related to a dead battery, not *cause* them. The issue lies elsewhere, and the alternator replacement might have uncovered a pre-existing problem or created a new one through mis-installation.

Here are the most likely culprits:

* Incorrect Alternator Installation: The most common cause. Double-check everything:

* Wiring: Ensure all wires are securely connected to the correct terminals on the alternator and the battery. A loose or incorrect connection can cause the system to shut down. Pay close attention to the positive (+) and negative (-) terminals.

* Belt Tension: The serpentine belt needs proper tension. If it's too loose, the alternator won't charge the battery. If it's too tight, it can damage the alternator or other components.

* Grounding: A poor ground connection somewhere in the charging system can prevent the car from running consistently. Check the ground straps from the engine block to the chassis.

* Battery Issues: Even with a new alternator, a faulty battery could be the problem. It might have been weak before the alternator replacement and is now unable to hold a sufficient charge. Test the battery voltage and have it load-tested.

* Wiring Issues (beyond the alternator): Something else in the charging system's wiring might be faulty. A corroded wire, a short circuit, or a blown fuse related to the charging system could all cause this. Check all fuses and relays related to the alternator and starting system.

* Other Electrical Problems: A failing ignition switch, a problem with the starter motor solenoid, or a malfunctioning PCM (Powertrain Control Module) could all cause intermittent starting or sudden shutdowns.

* Damaged components during alternator replacement: Did you accidentally damage any wiring, connectors, or components while removing the old alternator?

Troubleshooting Steps:

1. Visually inspect all alternator wiring and connections. Look for loose connections, corrosion, or damaged wires.

2. Check the serpentine belt tension. Ensure it's properly tensioned.

3. Test the battery voltage. Should be around 12.6V when the engine is off. Have it load tested at an auto parts store.

4. Check all fuses and relays related to the charging system.

5. Have a mechanic or auto electrician check the car's electrical system. They have the tools and expertise to diagnose more complex issues.

Don't continue trying to start the car repeatedly, as this can further drain the battery. Get it checked out promptly to avoid causing more damage.