One morning I came out to find my battery dead and had to jump it. I had the battery tested and they said it was still good. So they charged up the battery and it only took 6 minutes to reach a full charge. But even with the battery fully charged the engine takes longer to turn over like it doesn't haave enough juice. The lights dim under load. The alternator is a denso reman and is only a couple years old, when the car is running the voltage is approx. 14.3 volts. The only thing I know wrong is one of the ends on one of the spark plugs wires is damaged and no longer clips onto the spark plug. Sometimes it sounds like something is arcing when the engine is running. Could that faulty plug wire be the source of my problem?

 

It's a ground. My car did the exact same thing, I bought a brand new battery and it would kill it like it owed the car money. Without good grounds, the alternator won't charge the battery very well and will eventually lead to it being drained. I had the same "arcing" sound under the hood when the engine was running, and it was because 2 ground connections were starting to come loose. You could see where one of the terminals was starting to weld itself to the block.

There are 3 main grounds under the hood, called the "big 3". I come from the world of car audio, and the Big 3 is the first thing you do to a car before putting a big stereo in it so the electrical system can support it. If you want to upgrade the Big 3 under your hood, you don't even have to use the factory wires.. you can just make your own that tie into the 3 points.

Read this thread"
http://www.caraudio.com/forum/showthread.php?t=152355

 

I have had similar battery problems with my previous 1997 SC 400 and in my current 1999 SC 400. The problem is most likely not with your battery or the alternator.

I have found by replacing the factory cable connectors to the battery with Marine type LEAD connectors that are painted, except for the areas in contact with the battery post and cables will correct the problem!

I discovered after numerous dead battery situations in both cars that the alternator was putting out the required 14.2 V (the nominal value), but the battery was not charging. Therefore the only problem could be that the charge was not getting to the battery. I replaced the connectors with new factory connectors that were flimsy aluminum. This did not solve the problem.

I finally got a good conduction current into the battery after replacing the battery connectors with plain old lead type connectors that can be purchased at any pep boys for less than five bucks.

I have since utilized the Marine connectors in my 1999 SC 400, because they are painted on any surface other than connection to the cables and the battery terminal to prevent shorts.

Hopefully this will help correct your problem as well.

PS: my brother who is a certified mechanic actually uses spray paint or grease on the battery post after tightening the connection in order to prevent oxidation of the connection.

 

Alright. Thanks i will look into replacing the ground wires. I will do some searching on here to find out where they are.