Battery vs. Alternator

bryanjlane

About every 2 weeks, my car will start but will not idle and cut out. It will restart but again will not not idle and cut out again. Sometimes it will start and when I take off, it dies while I am driving. Other times it won't start at all and the battery completley dies. I have to jump start it to get it running. After jump starting, it runs fine until the next episode. I have a 2003 Jeep Liberty Sport. Help! Do you think it the battery or possibly the alternator?

caribou1

Step0_Cable integrity inspection:
- Check that all large section cables are well connected.

Step1_Broken or dead battery (inside connection):
- Turn on the headlights after 'step1' = No lights, no horn, no chime means the battery is out or not connected properly.

Step2_Engine to chassis/body:
- When the starter motor refuses to run, check your engine ground to chassis connection by starting the engine using one jump start cable between the battery ground lug and the body of the alternator/engine (or connect to a lifting point). You can also instal another small section grounding wire between the engine and body. It will reveal an intermittent grounding problem by melting :shades:

Step3_Defective engine controller:
- Remove the 'Field' connector of the alternator and Start the engine. You can do a short test drive without re charging the battery and try the idling condition. The battery alone will provide a stable operating condition for the engine.

Step4_Defective alternator:
- Connect the 'Field' of the alternator and observe the behavior. If the voltage regulator of the alternator is defective and injects AC into your circuitry, this is enough to make your engine stall especially when you combine loss of compression+vibrations+loose connections.