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Discussion Starter #1
I've just put in my 3rd new battery in my stock 240z......well, not really stock. I've upgraded the ignition, but this problem happened before that also. And I had a pro do that for me.

My guess is that the alternator isn't able to charge the battery sufficiently. Any ideas?

I"m about to install an F54/e31 head and i want to do it right. What should i do about the alternator? What would be ideal for that setup? I've heard that a GM one would work...but don't know for sure.

Someone please help.

Tom
 

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Now is the battery dying at all times? When the car is on or off, or is just when the car is on? If it is dying when the car is on and off, there is a badd connection electrically that is using power at all times. What you need to do there is take out every fuse one at a time and ahve a multimeter nearby and measure to see if the voltage has dropped. When it does drop, that is the area of electrical you need to investigate to find your problem. If it is only dying when the car is on, then that means the alternator is bad. If you have already replaced the alternater, check the wires to the alternator, could be fried and drive you nuts looking for something else(personaly experience with van).

My last comment would be on the E31 head. Is this a racing application? For street that comp ratio is somehwere betwwen 11-12:1 compression, that can mean some serious ping issues with normal pumpgas. Anyhow hope that other information provided helps you with your problem.

-Emir
 

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What happens is that the car starts and runs fine for a couple of months. And then I turn the car off and it won't start. The battery is dead!

I take it back and it's so drained that it gets replaced. It sounds to me that it's not getting recharged properly. Wouldn't that be the alternator's job?
 

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Yes, that is the job of the alternator and the voltage regulator.

If they both test out as functioning as per your Factory Service Manual then start checking your wiring connections.

Wayne Monteath
Masham, Quebec.
 

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Was the battery dead, and unable to take a charge? If your alternator was unable to charge the battery, the battery will be OK, just needs a charge. If they replaced the battery, it's possible that your alternator is over charging the battery and destroyed it. Batteries cannot be hurt by undercharging, unless you leave them dead for a couple days. An easy way to tell is to check the voltage at the battery when the car is running, rev it a little and watch it the whole time. 13.6 to 15V is normal range, but anything over 14 I'd suspect the regulator, which controls the alternator.
Any Pep Boys or Kragens should be able to help you test the alternator/regulator, Multi-meters start at about $20.00, and are a very helpful tool.

Chrome
 

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I had this EXACT problem years ago, but with a 70 Chevy Nova. I had bought a Sears Die-Hard and had gone all out and bought the "best" one. I proceeded to kill 3 in about 4 months. The manager at Sears finally told me that he couldn't continue to replace for free if there was something wrong with my car. I countered that each and every time they had had the car, they had supposedly done a "complete" electrical check and found nothing wrong. He then referred me to an "expert" on auto electrical systems.

I drove to this guys house, (yup, worked out of his garage) I got out, explained the problem and that I had been referred to him by the manager at the Sears Automotive shop. With that said, he had me open the hood, then with a phillips screwdriver disconnected the grounding wire from the negative post to the body at the body connection. He fished out a bit of sandpaper, sanded the area for the screw, and reconnected everything back up. He then turned to me and said, "You're done, that'll be $20."

I was flabbergasted, and I asked him about it, he said that it was a common problem, and that THAT lack of a contact causes all of the electrical items attached to the BODY to not receive a proper ground. The items then "find" a new ground, usually the engine or transmission, and since the drain is now heavier on the engine side than on the battery, the regulator gets fooled into NOT charging the battery. He also stated that I shouldn't explain to the folks at Sears what he was doing, as it was the easiest $20 bucks he made, apparently about 1-2 times a week.

The circuitry will check out fine on their testing units, and you won't notice problems as you get the battery replaced, but it won't be charged.

Check that wire out, it may be a fluke, but that may be all it needs.

FWIW
 
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