14 hours ago, dtejada said:

Something else must be wrong, I tried this and I’m getting 12.7V idling no accessories or lights on, I think that’s kind of low?

Are you using a meter or guessing from the dash gauge?

Measure at the battery as you increase engine RPM. That will tell you if the wiring is correct. Voltage will increase with RPM. 12.7 is an odd number on a running engine because there is a draw from the ignition system. Even a fully charged battery would probably show less than 12.6 on a running engine with no charging from the alternator. 12.7 implies that there is charging, which would mean the wires are correct.

If the wiring is correct then you might just have a weak alternator. I swapped a new aftermarket unit for a used 280ZX alternator and idle RPM voltage increased substantially. The aftermarket alternator was just weak at the speed the 280Z pulleys gave it at idle.

Where did you source the ZX alternator and did you have it checked at the parts house before installing whether it’s rebuilt or used?

53 minutes ago, Yarb said:

Where did you source the ZX alternator and did you have it checked at the parts house before installing whether it’s rebuilt or used?

Is this for me? I got the ZX alternator from a salvage yard off of a ZX. Looked like original equipment, probably had 80,000 miles on it, guessing. Did not have it checked. The aftermarket alternator was from OReilly Auto. I took it back and exchanged it for another aftermarket alternator which I put on the shelf for future use. It never got used.

For the individual that started this thread.

4 hours ago, Zed Head said:

Are you using a meter or guessing from the dash gauge?

Measure at the battery as you increase engine RPM. That will tell you if the wiring is correct. Voltage will increase with RPM. 12.7 is an odd number on a running engine because there is a draw from the ignition system. Even a fully charged battery would probably show less than 12.6 on a running engine with no charging from the alternator. 12.7 implies that there is charging, which would mean the wires are correct.

If the wiring is correct then you might just have a weak alternator. I swapped a new aftermarket unit for a used 280ZX alternator and idle RPM voltage increased substantially. The aftermarket alternator was just weak at the speed the 280Z pulleys gave it at idle.

Using a meter, I haven't increased RPM and checked voltage. I bought there alternator new from Zcardepot, came with testing slip.

Here is how I hooked up the alternator, green wire to the yellow 12v and red to the b+. Voltage regulator plug (car side) jumped pins 1and 5 pins 2 and 3. 🤔

4 minutes ago, dtejada said:

I haven't increased RPM and checked voltage.

That should be your next test.

You can also check for voltage at the two pins in the T connector with the key on, engine off. They should both have voltage.

11 minutes ago, Zed Head said:

That should be your next test.

You can also check for voltage at the two pins in the T connector with the key on, engine off. They should both have voltage.

12v on both pins but not change in voltage with rpm increase.

Measure voltage at B+ on the back of the alternator with the engine running. It should be charging if it has power on the two pins and the alternator pulley is spinning. Rev the engine while you're measuring.

Also measure resistance from the alternator body to the negative terminal with the engine off. It needs a good ground in addition to power at those pins.

And, this happens, sometimes the connectors inside the T connector are loose. Make sure you have a tight connection there.

2 minutes ago, Zed Head said:

Also measure resistance from the alternator body to the negative terminal with the engine off. It needs a good ground in addition to power at those pins.

And, this happens, sometimes the connectors inside the T connector are loose. Make sure you have a tight connection there.

6 minutes ago, Zed Head said:

Measure voltage at B+ on the back of the alternator with the engine running. It should be charging if it has power on the two pins and the alternator pulley is spinning. Rev the engine while you're measuring.

No voltage change with revs here, alt is turning for sure and the alt body has good ground just checked

Edited April 15Apr 15 by dtejada

I just looked at your picture. You have it set up in "one wire" fashion (maybe, I need to know where the white with black goes to). Why?

You didn't say where you're measuring at. The B+ terminal or the battery. Can't tell where your wires are going.

Could still be a wiring problem.

5 minutes ago, dtejada said:

No voltage change with revs here,

Edited April 15Apr 15 by Zed Head