ok so i have a 1988 rs, and the battery might be totally useless, if i try to start it for the first time over night it turns over and will run for maybe 3 mins and then die. if i try to start it after that it wont even turn over. sounds like a battery problem im just worried about the running for 3 mins than dieing part. it never used to have this problem till recently


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the car has been sitting for probly at least 3 years not doing anything as well
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and the car died when it was idleing

 

Try charging the battery, starting the car and monitoring the battery voltage at the battery terminals as the car is running. I would expect about 14.5 volts while the engine is running. As the car warms up and you approach the 3 minute mark notice if the voltage at the battery terminal is dropping as the time is elapsing. Maybe the battery charge requirement is too much of load for an idling engine.

Or keep the engine at an rpm where it is not at the lowest idle and see if it keeps running past the three minute mark. In this case you would be charging at a higher speed than idle. If it keeps running then maybe it means the battery needs replaced before you do any further analysis.

 

Do like CamaroRider says. If the battery has been sitting for 3 years w/o being charged then it's surely damaged. Strange phenomenon though. If the voltage never rises (over 12.0 V) when the engine is running then the alternator might not be charging.

 

12.6 volts is what a battery should have when it tests good.