* Weak Battery: A weak battery might not have enough power to start the engine, especially if the AC is on (which draws significant power). Jumping it temporarily solves the starting issue, but if the battery isn't charging properly, it'll quickly drain again.
* Alternator Problem: This is the most likely culprit. The alternator charges the battery. If it's failing, the battery won't recharge, and the car will stall once the battery's initial jump-start power is depleted. The AC compressor adds load, making the problem more apparent.
* Voltage Regulator Problem: The voltage regulator controls the alternator's output. A faulty regulator can cause the alternator to either overcharge (damaging the battery) or undercharge (leaving the battery depleted).
* Other Electrical Issues: Less likely, but a short circuit somewhere in the electrical system could drain the battery rapidly, leading to similar symptoms.
What to do:
1. Have the battery and alternator tested: A reputable auto parts store or mechanic can perform these tests quickly and relatively inexpensively. This is the most crucial step. Don't just assume it's the battery based on symptoms alone.
2. Check the battery terminals and connections: Corrosion on the terminals can restrict current flow and cause starting problems. Clean them if necessary.
3. Inspect the belts: Make sure the alternator belt is properly tensioned and not cracked or worn. A slipping belt can prevent the alternator from charging properly.
In short, while a bad battery is a *possible* cause, the stalling after a jump start strongly suggests a charging system (alternator or voltage regulator) is the more probable cause. Get it tested professionally to pinpoint the exact problem.
