1975 280z New ZX Alternator Not Charging

[jtcn]

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/alternatorswap/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 came out to check out the car and 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.

[jtcn]

While waiting for my post to get approved I went out and did some voltage tests, just for reference.

 

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.

[banzai510(hainz)]

so your saying you went from a External VR sytem to  Internal volt reg alternator?

 

 

when a Car overvolts it the VR most times.  I just change out the VR on my 510 as I use the external VR and alternators.

 

Now if you got a Alternator mixed up from the store I seen this happen a IR type still in a ext type and the wire not modified.

 

 

Im not a Z expert so cant give dates when they went to a IR type alternator

[jtcn]

so your saying you went from a External VR sytem to  Internal volt reg alternator?

 

 

when a Car overvolts it the VR most times.  I just change out the VR on my 510 as I use the external VR and alternators.

 

Now if you got a Alternator mixed up from the store I seen this happen a IR type still in a ext type and the wire not modified.

 

 

Im not a Z expert so cant give dates when they went to a IR type alternator

Yeah Z cars were externally regulated until '78, when they switched to IR.

The ZX alternators are all internally regulated and I wanted to swap because it's a common upgrade, so I figured why not.

I'll look up if there's a way to tell if an alternator is IR, but I'm 99% sure it is.

[datzenmike]

78 and up all switched to internally regulated alternators.

 

 

 

This is how I converted my 710 and 620. Only two pairs of wires. I don't know if the Z cars had the same wire colors.

 

White/Red stripe to White/Black stripe

White to Yellow.

[jtcn]

78 and up all switched to internally regulated alternators.

 

 

 

This is how I converted my 710 and 620. Only two pairs of wires. I don't know if the Z cars had the same wire colors.

 

White/Red stripe to White/Black stripe

White to Yellow.

The wires were different for pretty much every year on the Zs.

I think I got my wiring right, I did it exactly the way the guide said to.

I feel like the problem might be that my "L" connection is only getting 11.7v when its supposed to get 12v.

I've been dealing with this for about a week now.

[datzenmike]

 

I soldered Green/Red to White/Black.

And I soldered White to Yellow.

 

 

Green/Red to White/Black. is the only difference. What other color wires do you have?

[jtcn]

Green/Red to White/Black. is the only difference. What other color wires do you have?

The only others were solid green and black.

[datzenmike]

Got a picture of the volt regulator where you cut the wires?

[jtcn]

No, but I cut the wires at the wire harness right before the connectors to the voltage regulator.

I can go out and take a picture if you want me to

[datzenmike]

Sure. What I did was cut the regulator off it's plug, join the wires and just plug it back onto the harness. I'm hoping the wires on the plug are all the same.

[DanielC]

Look at the back of the alternator, where the two small wires for the "T" connector plug in.  If they are marked "F" and "N" you have an externally regulated alternator.  If they are marked "S" and "L" it is an internally regulated alternator.

[jtcn]

Look at the back of the alternator, where the two small wires for the "T" connector plug in.  If they are marked "F" and "N" you have an externally regulated alternator.  If they are marked "S" and "L" it is an internally regulated alternator.

Yeah it definitely says S and L.

Do you guys have any thoughts on why the "L" connection on the T connector is only getting 11.7v?

[datzenmike]

I believe that is wired through your red CHARGE lamp so you won't measure the full 12.6 volts..

[jtcn]

I believe that is wired through your red CHARGE lamp so you won't measure the full 12.6 volts..

Here's the thing, my car doesn't have a red charge lamp. It has the ammeter like on 240z's.

Also, I charged my battery full and I tested the wire. It got 12 volts and it still doesn't charge the battery...

[datzenmike]

Pretty sure it should have one. Turn ignition to ON it should light up to test/show it's working. All other Datsuns have this and it's how the alternator is primed to start charging.... no light... no charge. Maybe the Z cars are different.

[banzai510(hainz)]

the link with a drawing shows a charge warning lamp.

linkalso shows:

 photo of the wires jumpered. It looks like the Moron did it on the harness side instead of doing it on the voltreg side so all you go to do is plug the old volt reg or another one back in if you find a old type alternator(go back to stock)

[jtcn]

the link with a drawing shows a charge warning lamp.

linkalso shows:

 photo of the wires jumpered. It looks like the Moron did it on the harness side instead of doing it on the voltreg side so all you go to do is plug the old volt reg or another one back in if you find a old type alternator(go back to stock)

Lol you can do it either way. The harness-side of doing it just makes it permanent.

Pretty quick to call me a moron when you said yourself you're "not a z expert"

Stick to what you know if you're gonna be a dick.

[jtcn]

Pretty sure it should have one. Turn ignition to ON it should light up to test/show it's working. All other Datsuns have this and it's how the alternator is primed to start charging.... no light... no charge. Maybe the Z cars are different.

Here's a pic of what my gauges look like.

Here's a pic of a Z car with the charge light.

Would I be better off posting this on the Z car part of the forums?

[DanielC]

Simple internal regulator alternator test.

Bolt it on engine, with belt.

Make sure there is a ground wire from alternator frame to negative battery cable, and to negative battery terminal.

Put one test light lead on the positive battery post.  Touch the positive output terminal on the alternator.  If the light lights up, the diodes in the alternator are bad, get another alternator.

 

Make sure there is a connection between alternator positive output to positive battery terminal

Hook up a wire to the "L" terminal. 

With the engine NOT running, touch test light probe to the wire on the "L" terminal.  The test light should light.

Start the engine.  Touch the test light again to the wire on the "L" terminal.  You might see a brief flash of the test light. 

Check battery voltage.  It should be 13.5 to 14.5. 

[jtcn]

Simple internal regulator alternator test.

Bolt it on engine, with belt.

Make sure there is a ground wire from alternator frame to negative battery cable, and to negative battery terminal.

Put one test light lead on the positive battery post.  Touch the positive output terminal on the alternator.  If the light lights up, the diodes in the alternator are bad, get another alternator.

 

Make sure there is a connection between alternator positive output to positive battery terminal

Hook up a wire to the "L" terminal. 

With the engine NOT running, touch test light probe to the wire on the "L" terminal.  The test light should light.

Start the engine.  Touch the test light again to the wire on the "L" terminal.  You might see a brief flash of the test light. 

Check battery voltage.  It should be 13.5 to 14.5. 

Unfortunately I don't have a test light.

Is there a way to do this but with a voltmeter? If not I can just go buy a test light tomorrow if I have to.

Do I need to look for one like this? http://www.autozone.com/test-scan-and-specialty-tools/test-light/innova-transparent-handle-test-light-circuit-tester/186543_0_0

Thanks for the instructions.

[banzai510(hainz)]

I dont have to be a Z expert to figure out its ezer to cannibalize the VR side of the connector and make jumpers.

 

 

Just hate seeing haked up Datsuns wiring. Its seems to be a common thing.

[jtcn]

I dont have to be a Z expert to figure out its ezer to cannibalize the VR side of the connector and make jumpers.

 

 

Just hate seeing haked up Datsuns wiring. Its seems to be a common thing.

Whether it's easier or not it still gets the job done.

I could still splice the connector back on if I absolutely had to but I definitely don't plan on going back to external regs.

Well I hate seeing datsuns not running more than hacked up lol

I just wanna get back on the road and this problem is extremely frustrating.

[jtcn]

So I was reading a forum post about problems with the ZX alternator swap on the '75 years and found this comment.

 

"Found this on a search since I am swapping a turbo engine and ZX Alternator into my 75 (1/75 build date). 

 

I had 6 wires and they were different than any of the 3 write-ups I found online.  I ended up following the OP's direction and ended up jumping 2-3 and 5-6 with a diode in the 5-6 splice since it was key-on hot.

 

My conclusion is that Datsun changed wiring frequently.  Don't just count terminals and think it will work.  Verify what you have at each wire before splicing."

 

I have the same build date as him, so tomorrow I'm going to undo all my wiring (again) and verify what all of the wires do and splice accordingly.

 

Edit: Here's the link to the thread if anyone is wondering. http://forums.hybridz.org/topic/108455-75-280z-alternator-upgrade-to-zx/

[DanielC]

You need a test light.  It needs an incandescent lamp in it, and should draw about 300 milliamps.  I think the Autozone one is good