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JTCN

1975 280z New ZX Alternator Won't Charge

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softopz    12

Dont undo your wires. Now start the car and see what the alternator is charging at pos and earth. then unplug T connector see if it changes. I took the the time to write a step by step process to fully diagnose your charging system you only did half of it and your asking for suggestions " ideas or tests"

 

 Search how to use resistance on multimeter watch a video on youtube to see some functions of a multi meter. While your at it search how to diagnose alternator, and charging system I give up spoon feeding  for today.

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NewZed    56

Okay so I just went out to check with the meter with my dad and we found out that the earth on the alternator is getting 12v from the positive on the battery.

The BAT terminal is getting 0v from positive, and 12v from negative.

It seems to me, based on the way you're writing, that you might not really understand how to measure voltage.  No offense.  But your word usage is not the way a person experienced in these things would write.

 

Voltage is not gotten.  It just exists across points in a potential circuit.  " earth on the alternator is getting 12v from the positive on the battery".  

 

It looks like you put one probe on E and the other on the battery positive terminal and saw 12.  That would be a correct reading for proper wiring.

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NewZed    56

And all of your measurements in Post #25 look correct.  Your comment in #26 doesn't fit what you saw.  Everything looks fine.  BUT.  You didn't show the measurements at the T plug.

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NewZed    56

Since you did say earlier that you saw battery voltage at the bottom leg of the T plug and everything else looks good here's something that happened to me a few years ago - the T plug connector was loose and dirty.  It wasn't making electrical contact.  I found that I could wiggle it to a new spot and the alternator would start charging again.  It was an odd thing.  A quick squeeze with some needle-nose pliers fixed it.

 

Make sure the T plug is making good contact with the alternator terminals.

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JTCN    0

Alright sorry I stayed at a friend's house last night and didn't get to try anything.

 

 

Dont undo your wires. Now start the car and see what the alternator is charging at pos and earth. then unplug T connector see if it changes.

Just tested with the car running, alternator is only charging 11.8v. (I put + on BAT and - on negative battery) Pulled the T connector and nothing changed.

 

 

I took the the time to write a step by step process to fully diagnose your charging system you only did half of it and your asking for suggestions " ideas or tests"

I wanted to compile a bunch of tests and suggestions to try out while I wasn't home, only had time to do half of your suggestions, my bad.

 

 

While your at it search how to diagnose alternator, and charging system I give up spoon feeding  for today.

I'll do that. Thanks anyway

 

 

It seems to me, based on the way you're writing, that you might not really understand how to measure voltage.  No offense.  But your word usage is not the way a person experienced in these things would write.

 

Voltage is not gotten.  It just exists across points in a potential circuit.  " earth on the alternator is getting 12v from the positive on the battery".  

 

It looks like you put one probe on E and the other on the battery positive terminal and saw 12.  That would be a correct reading for proper wiring.

You're absolutely right I'm not experienced in electrics lmao.

My dad talked to an electrician friend and he explained it. Pretty embarrassing lol

 

 

And all of your measurements in Post #25 look correct.  Your comment in #26 doesn't fit what you saw.  Everything looks fine.  BUT.  You didn't show the measurements at the T plug.

Just tested with the key on, Top of the T was getting 12.4 and the bottom was getting 11.8

Key off the top of the T was getting 12.4, bottom was getting 0

 

 

Since you did say earlier that you saw battery voltage at the bottom leg of the T plug and everything else looks good here's something that happened to me a few years ago - the T plug connector was loose and dirty.  It wasn't making electrical contact.  I found that I could wiggle it to a new spot and the alternator would start charging again.  It was an odd thing.  A quick squeeze with some needle-nose pliers fixed it.

 

Make sure the T plug is making good contact with the alternator terminals.

Yeah funny thing, I was trying to test the bottom of the T plug and I had to seriously get the probe in there to get a reading.

I've already sprayed contact cleaner on the T plug yesterday but maybe it wasn't enough.

And don't worry I think I'm testing voltage the right way now lol...

 

So we're still where we left off, alternator isn't charging (or at least not charging enough).

I guess I'm going to charge my battery and look into what else to try.

 

Edit: I also soldered all my connections this time.

Edited by JTCN

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JTCN    0

Something else I wanted to bring up.

What is the possibility of this just being a bad alternator? I took it to autozone to get tested and it passed but I'm not sure if I can really trust that right now.

When I switched from my old alternator+voltage regulator the only thing I did was splice the harness together the right way and hook up this new alternator.

Should I just send this thing back and try another? I'm conflicted because it passed the autozone tests.

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JTCN    0

I haven't updated this thread but here is whats happened so far.

Im gonna send this alternator back to the seller and while I was waiting I went ahead and ordered one from autozone.

I got the new alternator (still a remanufactured one) and installed it.

It's doing the same shit as the other alternator. 11.8v output from it.

But I discovered something after doing more tests with the voltmeter.

 

KEY OFF:

12.4v at car battery

12.4v at top of "T" connector. (also known as "Sense" connection)

0v at bottom of "T" connector. (also known as "Lamp" connection)

12.4v at alternator BAT terminal.

 

KEY ON:

12.2v at battery

12.2v at top of "T" connector ("S" connection)

11.7v at bottom of "T" connector ("L" connection)

12.2 at alternator BAT terminal.

 

So in the swap guide I mentioned it says this:

"1. An "L" connection which goes to a "switched" 12V supply. By this I mean a 12V source that is active only when the ignition switch is in the ON position. I use the mnemonic "L" for "lamp", the alternator warning lamp (if used) is in series with this connection. This terminal also supplies the "excitation" current to the alternator field winding at engine turn on, allowing the alternator to begin producing voltage as the engine is ramping up to idle speed. Once the alternator rotor is turning fast enough, it generates it's own supply for the field winding and the current in the "L" connection stops flowing. The warning lamp (if used) goes out."

 

So when the key is on, the "L" connection gets 12 volts, which gets the alternator to charge.

My connection is only getting 11.7v. Could that be why it's not charging? I have the car battery on a charger right now in case it's not charged enough to supply the right voltage to this connection.

But everything else is getting 12.2v when the key is on... What's the first place I should look to find out why it isn't getting 12v?

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NewZed    56

Everything in 35 looks right. You didn't show that you have a good grounding of the case though. And you didn't show the values with the engine running. But the measurements shown look correct.Not sure what's happening.

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Miles    32

I just searched HybridZ for the ZX alternator which returned 356 results. On the the first two pages were threads with the answers to your problem. Some of the threads include references to other Z websites detailing the ZX alternator swap. Included in the threads are pictures, schematics and tables showing the correct wiring.

 

 

Persistent searching pays off.  Listen to what this guy does:

 

Edited by Miles

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JTCN    0

Everything in 35 looks right. You didn't show that you have a good grounding of the case though. And you didn't show the values with the engine running. But the measurements shown look correct.Not sure what's happening.

Someone in another forum showed me a thread on testing IR alternators and I think I'll try that next.

Here's the link: http://community.ratsun.net/topic/65156-testing-an-internally-regulated-alternator/

But first I'll need a test light.

In the meantime I'll go check the ground on the case and do voltage tests with the car running

 

Edit: By the way, I read from a guy that has the same year and build date as me that you can't trust the wire diagrams.

He said datsun switched up their wiring colors and the placement of which wires constantly and that I should check and verify what each wire does before splicing.

I was planning on doing that but I figured if I'm getting the correct voltage with key off and key on, wouldn't that mean my wiring is fine?

Edited by JTCN

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JTCN    0

GOOD NEWS EVERYONE!

I started the car just a minute ago and checked voltage at some areas and after I finished I decided to leave it for a few minutes for it to warm up.

After I got back it was fully warmed up and I tried revving it to 4K rpm and I saw the ammeter jump up!!!

I jumped out the car and checked the battery its getting 13.5v consistently at idle! Even with a bunch of accessories on!

I have no idea why it finally started charging. I guess it needed a jump start.

I tried revving it up before but this time it decided to work.

 

Thank y'all for helpin!

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