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Discussion Starter · #1 ·
My 75 280's zx alternator died, so i bought a new one, and i had it running for a couple days, but then suddenly it will not run without jumper cables attached. After jumping the car and takling tyhe cables off, i measured the battery and it reads 11.9 volts. This cant be a problem with the alternator or its wiring, becuase if so, the car wouldve sputtered out and drained the battery, instead of instantly dieing and leaving the battery mostly charged, right? Ive been struggling with this problem for a couple weeks now, any suggestions or help would be great!
 

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1983 280ZX Turbo
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The battery is low at present. I don't think you can determine anything without charging it up in full, then running it and testing the charging system with a multimeter. There are plenty of videos on YouTube with the simple procedure.
 

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Your troubleshooting pathway: Battery, starter, alternator and fusable links/wiring....

Agree with the above response that your battery is a bit low. You'll need to charge your battery with your 110v battery charger before proceeding further.

A starter that is going bad will draw more amperage than usual could account for your problem. I keep an accessory 12 volt plug in voltmeter in all my cars and it was a great troubleshooting aid while starting / driving and helped me narrow my problem (Maxima) to the starter.

In my experience, alternators either work or they don't - (provide a charge or not), thus troubleshooting them is typically straightforward.

Let us know what eventeventually find out.
 

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It is possible for the alternator to die trying to charge the week battery. The battery should be recharged from an external source before putting with the new alternator.

Also, aftermarket and remanufactured parts really suck anymore. I went through 4 alternators for my 4Runnner before I got a good one.


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8 / 71 240Z, HLS30-40031, L24-052899, Sunshine Yellow
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I don’t know if this applies to a ‘75 280Z, but check this thread.
 

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Discussion Starter · #6 ·
The battery is low at present. I don't think you can determine anything without charging it up in full, then running it and testing the charging system with a multimeter. There are plenty of videos on YouTube with the simple procedure.
Did that, car can run and drive now, but now I am getting a very strange overcharging problem. Wheni start and run the car from 12.8V, my output while idling is roughly 13.5 - 14.5, but after i turn the car off, The voltage at the battery is way too high, around 13.05-13.3V. Then, if i start the car with the battery voltage still too high, the voltage on the car while it is running is anywhere from 14.5-15V. Any help would be appreciated.
 

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Discussion Starter · #7 ·
Your troubleshooting pathway: Battery, starter, alternator and fusable links/wiring....

Agree with the above response that your battery is a bit low. You'll need to charge your battery with your 110v battery charger before proceeding further.

A starter that is going bad will draw more amperage than usual could account for your problem. I keep an accessory 12 volt plug in voltmeter in all my cars and it was a great troubleshooting aid while starting / driving and helped me narrow my problem (Maxima) to the starter.

In my experience, alternators either work or they don't - (provide a charge or not), thus troubleshooting them is typically straightforward.

Let us know what eventeventually find out.
Charged the battery and the car can run and drive now, but now I am getting a very strange overcharging problem. When I start and run the car from 12.8V, my output while idling is roughly 13.5 - 14.5, but after i turn the car off, The voltage at the battery is way too high, around 13.05-13.3V. Then, if i start the car with the battery voltage still too high, the voltage on the car while it is running is anywhere from 14.5-15V. Any help would be appreciated.
 

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1983 280ZX Turbo
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Did that, car can run and drive now, but now I am getting a very strange overcharging problem. Wheni start and run the car from 12.8V, my output while idling is roughly 13.5 - 14.5, but after i turn the car off, The voltage at the battery is way too high, around 13.05-13.3V. Then, if i start the car with the battery voltage still too high, the voltage on the car while it is running is anywhere from 14.5-15V. Any help would be appreciated.
Yes, all of this is normal voltage.

At rest your battery should be around 12.4 to 12.5V so it's a couple of tenths high, but I view that as good news. If the battery drops under 12V most cars won't start.

When running at normal engine speed, voltage should be around 14.5V. Yours is a bit high, but if the battery was charging actively, I'm not surprised.

Drive it.
 

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Discussion Starter · #11 ·
Yes, all of this is normal voltage.

At rest your battery should be around 12.4 to 12.5V so it's a couple of tenths high, but I view that as good news. If the battery drops under 12V most cars won't start.

When running at normal engine speed, voltage should be around 14.5V. Yours is a bit high, but if the battery was charging actively, I'm not surprised.

Drive it.
No complaints about that lol will do
 

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Some of the Z's run the Brake Check Lamp Warning Relay power through the regulator. On the 76 cars you can end up with the relay powered all of the time after wiring for the conversion. This will kill your battery in a day or two. You can confirm by listening for the click of the relay, under the passenger seat, when you disconnect and reconnect the battery. vidmate save insta
 
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