Charging issue

[Dan Ireland]

Ok, got a 2005 LS. Wonderful car ,love this thing. But of course its been plagued with a few issues since I purchased it for my wife. Currently every so often the battery goes dead. Since getting it and joining this forum I've learned how they can be issue prone. So ,aside from the more obvious issues concerning charging is there anything about the charging system that I may need to know about? Basically its run fine for a couple weeks. Wife leaves early some mornings for work, this morning it wouldn't start. Done it before... I put the charger on , does great for a couple weeks. Battery is new, couple weeks old. Alternator is putting out the right voltage.... Not sure if theres a short, or if shes leaving something on , or if it could be something inherent to the vehicle. Any advice welcomed and appreciated.

 

[joegr]

You have at least two possible cause areas for this.
1. Your charging system is intermittently failing.
2. You have an intermittent parasitic drain.

Troubleshooting (1) is not too bad. I'd plug a volt meter in and glance at it while driving for at least a few days. If it goes below 14 with the engine running, it is probably the issue. If it goes below 13, it is clearly the problem. After that, there is some troubleshooting to narrow it down to the alternator, wiring, or PCM. Most everyone skips that (even me), because it is almost always the alternator itself.

Troubleshooting for an intermittent parasitic drain can be a nightmare...

 

[04_Sport_LS]

And proper charging voltage should be approximately 1.5 volts over the battery voltage when not running.

You may want to check for corrosion on the ground terminal, (negative cable), where it bolts through the trunk floor. You may find that there is corrosion there... preventing a good ground.

If that is the case... be careful though. Since that bolt goes through the trunk floor... the threads are exposed to the elements and will rust.

Without cleaning the threads and soaking them with PB Blaster... the bolt head will most likely twist off... causing more aggrivation.