Ok, so I've been walking out to my 240 only to find it has a dead battery and so I am working on capturing the culprit.

The battery receives a charge during engine operation between 13 and 13.5 volts.

Output at the alternator poles ranges from 13.5 to ~14.25 volts.

Next I tested the "charge relay release voltage" by probing the N position of the connector (yellow wire). My voltmeter read 8v at idle and 10v at 1200 RPM. The FSM says this wire should only receive 4.2 to 5.2 volts at this terminal.

So, based on my extremely high readings, what would any of you suggest?

I removed the voltage regulator a few days ago to clean connections. I was under the impression that it was a servicable, breaker type regulator BUT it looks as if it is sealed with a green gelatin-like insulative on the back of the housing... so I just put it back on the fender.

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1973 Datsun 240z - "Owning the streets of Vacaville for 35 years!"
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"Junk" yard? ...Or treasure yard? If it makes you feel better, you're recycling!
Great for the environment, great for the wallet.
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Caught somewhere between "all fun & games" and jail time.

Check 1.5 feet up from the alt in the wire loom. The charging wire needs to be spliced or replaced. I have seen these get down to about 4 strands. To prove this just add a temporary wire from the battery positive to the alternator output stud. THERE SHOULD only be about .25 volts MAX from the battery plus TO the alternator output. Since the engine "wiggles" the copper in the wire breaks. NK



Edited 2 time(s). Last edit was february 08, 10:45pm.

Why don't you check the "health" of your electrical system with the car off? Connect an ammeter to the battery to measure the current with the car off. If you have more than a few milliamps, then you probably have a circuit energized that is draining your battery. If your battery is draining overnight, it's probably a pretty good load, or your battery may just be getting old.

Look for the usual culprits that cause a battery drain:
Voltage regulator
Alternator short
Dome light
Glove box light
Added stereo/alarm
Short in the engine wiring harness or body wiring harness.

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Norm,

I will try the jumper test and I will also look out for that possible decayed wire.

Steve,
it's funny you mention the dome light, because now that I htink about it... I believe I've had to replace that bulb twice within the last year alone. I will check it out and see if the POS lead on the light is contacting metal. Although, then again... I don't leave the door open for days on end. Am I missing something here?

The glove box light currently has no bulb due to the glove box door being broken and not depressing the light button.

I open to the possibility of it being the VR... not the alternator so much but, hey I guess $hit can happen. I'll try nrkrel's test and, if inconclusive, will leave the battery hooked up but with certain components unhooked (VR, alt, starter, dome light).

I know the stereo is good. I have the center dash gutted because of a 240 to 280 gauge change (but I can GUARANTEE that this project is irrelevant to my current woes, no pun intended). Time to go find an ammeter out in dad's "mess".

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1973 Datsun 240z - "Owning the streets of Vacaville for 35 years!"
------
"Junk" yard? ...Or treasure yard? If it makes you feel better, you're recycling!
Great for the environment, great for the wallet.
------
Caught somewhere between "all fun & games" and jail time.

Hahaha YES! I think I figured it out!!!

I took a simple test light (not powered) and bridged it between the unhooked negative battery cable and the negative battery post. Theoretically, a ground wire should not have 12 volts runing through it... thus, when I test light it to the neg post the ligth should NOT come on. Well guess what? It did!

BAM MOTHER F***ER! So I started plucking fuses and running back to the battery to perform my cute little test. So which circuit is it?

Winning answer goes to Mr. Steve! That mother-lovin' dome light! POS I shoulda known... that thing ate bulbs left and right and then stopped working altogether.

Now its just a question of where the screw up is at. My guess is the steering lock switch. For whatever reason that ties in to the dome lamp circuit and is the ONLY portion of the circuit that I have played with. I have a feeling I hooked something up wrong.

I'd fix it now, but I gotta take a nap before class tonight. I only got 3 hours of sleep on a crappy headache last night and just got home from work. But I'll finalize this thread when I have a concrete answer. Peace!

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1973 Datsun 240z - "Owning the streets of Vacaville for 35 years!"
------
"Junk" yard? ...Or treasure yard? If it makes you feel better, you're recycling!
Great for the environment, great for the wallet.
------
Caught somewhere between "all fun & games" and jail time.