1975 280z New ZX Alternator Not Charging - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 8 (permalink) Old 02-13-2017, 06:43 PM Thread Starter
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1975 280z New ZX Alternator Not Charging

Get ready because this is gonna be a long post. First let's go from the start.

I recently found out my voltage regulator went out on my Z.
It was allowing the car to hit 16v+ at the battery.
So I looked up replacing it but decided I would do the ZX alternator instead.
I ordered a remanufactured one off amazon and when it got here I went to work.
I followed this guide: http://atlanticz.ca/zclub/techtips/a...wap/index.html
The voltage regulator harness wires on my car are exactly the same as the ones for the 1975 year in the guide.
I soldered Green/Red to White/Black.
And I soldered White to Yellow.
Here's a pic of my wiring: http://i.imgur.com/U2LfjKV.jpg
I hooked up my alternator the same way it was on the original. Here's a pic of all my connections: http://i.imgur.com/fRSOvqZ.jpg

After doing all this I connected the negative battery cable back on the battery and got a spark, but I didn't think much of it.
I started the car with my voltmeter hooked up to the battery and noticed it wasn't charging.
I revved the car, took it around the block, nothing.
Battery voltage with car off is 12.5v
Battery voltage with car on and running is about 12.1v
The alternator just wasn't charging the battery. So I hooked up my meter's POS probe to the BAT terminal and my NEG probe to the negative terminal on battery. 11.8v
So I had my dad come check out the car and they he said that it was most likely a bad alternator and to get it tested/replace it.
I took it to autozone and it passed all 3 tests. But I decided to return the alternator and pick up a new one anyway.
Which brings us to today. I hooked up the new (still remanufactured) alternator and it's doing the exact same thing. 11.8v output.

I've done ALL kinds of voltage tests on the car and unfortunately I can't remember most of them, but I'll go back out and test again and write it all down and post back here.
The ONLY wiring I did was the 4 wires I spliced on the voltage regulator. The car was working fine before I did this swap it was just getting too much voltage from alt.
Also I've checked all my fuses and fusible links. They all look great and no obvious burning.
I'm really stumped on what to do next. I really need some help on where else to check and what tests I need to do to find out what exactly is going on.
I'd really appreciate and support or ideas you can throw my way, If you guys have any questions please post them and I'll answer as quick as I can.

Last edited by JTCN; 02-14-2017 at 02:35 PM.
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post #2 of 8 (permalink) Old 02-13-2017, 06:45 PM Thread Starter
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I just did some tests with the voltmeter, here are the results.

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 above this post 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?

Edit: Just something I wanted to mention, my '75 Z has an ammeter gauge and not a voltage gauge. As far as I know it also doesn't have an alternator charge light/warning light.
Edit2: I charged my battery fully and I got 12v at the "L" connection, but the alternator still isn't charging.

Last edited by JTCN; 02-14-2017 at 01:45 AM.
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post #3 of 8 (permalink) Old 02-13-2017, 06:49 PM Thread Starter
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It says I'm not allowed to post pictures or links because my post count is too low. I'll update the thread with pictures soon though.
The swap guide I followed is that one on atlanticz.
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post #4 of 8 (permalink) Old 02-14-2017, 01:11 AM Thread Starter
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Come on y'all not even a suggestion? Lol
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post #5 of 8 (permalink) Old 02-14-2017, 01:41 PM
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Have you checked voltages across the fusible links with the car running? They shouldn't drop any voltage at all, well maybe a few millivolts but not much. If you do see a voltage drop, pull the links and check them with an ohm-meter. They should read zero ohms. If there is resistance, clean the connectors, both on the links and on the receptacle and measure resistance again. If it doesn't go to zero, replace the links. If the links show zero resistance, reinstall and recheck the voltage drop to be pretty much zero. If you still get a drop, check the connections again.

Scott
Tucson, Arizona

9/74 260Z VIN RLS30 060061
Restored!
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post #6 of 8 (permalink) Old 02-14-2017, 02:33 PM Thread Starter
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Originally Posted by beg3yrs View Post
Have you checked voltages across the fusible links with the car running? They shouldn't drop any voltage at all, well maybe a few millivolts but not much. If you do see a voltage drop, pull the links and check them with an ohm-meter. They should read zero ohms. If there is resistance, clean the connectors, both on the links and on the receptacle and measure resistance again. If it doesn't go to zero, replace the links. If the links show zero resistance, reinstall and recheck the voltage drop to be pretty much zero. If you still get a drop, check the connections again.
Thanks for the suggestion. I'll go do that in a minute and report back.
Edit: Finally allowed to posts links. I updated the original post with my pictures and a link to the swap guide.

Last edited by JTCN; 02-14-2017 at 02:36 PM.
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post #7 of 8 (permalink) Old 02-14-2017, 03:07 PM Thread Starter
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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.

**** YEAH
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post #8 of 8 (permalink) Old 02-14-2017, 03:21 PM
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Quote:
Originally Posted by JTCN View Post
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.

**** YEAH
Congratulations, glad things are working now. Just as a precaution, if you did mess with your fusible links before things started working, you might have "partially cleaned" a connection simply by disturbing it a bit. It wouldn't hurt to do a good job cleaning the connections anyway and only takes a few minutes.

Another thing to note about these ammeter cars. If you add accessories that want to draw directly from the battery, your ammeter will not show the discharge due to those accessories. The way the ammeter works is that a shunt is installed in series with the battery and the ammeter reads the voltage across the shunt. The shunt itself is really a big piece of metal with a known but very low resistance. If you want your gauge to read correctly, all accessories (radios, amps, headlight relay kits, dash and marker light relay kits and so on) should be connected to the other side of the shunt. I installed a separate power strip in my car which allows simple connection to the "after shunt" power.

Starter relay kits IMHO are best connected directly to the battery as they aren't used except to start the car.

Scott
Tucson, Arizona

9/74 260Z VIN RLS30 060061
Restored!
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