HELP! Upgraded alternator in my '75 280z but headlights now won't work.

[nissanthanh]

It wasn't on the same 6 prong connector. It was part of the 3 (yellow blue green). The 6 prong connector had the green - red slot capped. Just like my original post stated same as other guy who posted on another forum and in hybridz

[Zed Head]

A thought that might help clarify - the writeups around the internet about wiring up an internally regulated alternator are just focused on two circuits. The L circuit which energizes the alt. windings and the S circuit which the internal regulator uses to regulate. The other wires are typically just left hanging,and un-needed. If a person wanted to they could probably just unplug the external regulator, leave the wires alone and run a switched wire to L and connect S directly to the battery.

But none of this probably matters to the headlight problem. There's no reason for your headlights to have stopped working. It's probably just coincidence and while the car sat the dimmer switch lost contact. Shoot some contact cleaner in to the dimmer switch at the base of the turn signal stalk.

Although - you never said that the alternator was actually charging, only that the engine runs. the engine will run from battery power alone. So, what is the ammeter doing while the engine runs?

[SteveJ]

It wasn't on the same 6 prong connector. It was part of the 3 (yellow blue green). The 6 prong connector had the green - red slot capped. Just like my original post stated same as other guy who posted on another forum and in hybridz

The three wire connector is for the AC. Have you tried to see if the green/red wire is on the C-6 connector? One of the issues is that the wiring diagrams show a seatbelt interlock relay system. I don't know when Nissan ditched it. You can find many threads about defeating them in the 74. The manual I downloaded from Xenons30 has too many artifacts to be truly useful.

On the 240Z, the black/white wire from the ignition was joined with the white/black wire. Wiring that way may get the alternator working. Then you could focus attention on the lack of headlights.

[nissanthanh]

Shat you're right...

[nissanthanh]

SteveJ, is the C-6 farther towards the front of the vehicle? I think it may be right past my 2nd photo. I'll take another shot when It's light out. Currently can't sleep because this is haunting me. But my photo is of my ammeter while car is just started. I'm assuming the ammeter should be in the +.

[SteveJ]

C-6 is under the dash. Of course, your ammeter is showing a discharge. You don't have the alternator hooked up properly, yet.

The biggest problem you are having right now is that you aren't focusing on one problem. You are getting suggestions about two issues (alternator & headlights) in this one thread, and it appears as though you may be bouncing back between the two.

Let's see if I can clarify the alternator issue for you.

1. You need wires from three locations going to a ZX alternator: Ground, battery, & ignition.

2. Your wiring harness was designed to utilize an external voltage regulator, therefore the harness requires some jumpers to re-route signals.

3. The white and yellow wires at that 6 pin harness should be jumpered together. That will give the new alternator the battery signal.

4. The white/black wire needs the ignition signal. Normally that would come from the wire at the #1 pin. According to the wiring diagram, that should be a green/red wire.

5. Since you don't have a green/red wire there, you need to get an ignition signal from somewhere else. The best alternative is probably the black/white wire coming off of the ignition switch. Trace that wire on the wiring diagram. One of the places it shows up in the engine bay is at the "Emergency Start Switch" that appears to have been deleted. If the harness was built to the wiring diagram, there should be a 4 pin connector in the engine bay on the passenger side with that wire.

The thing that concerns me is that if you didn't have the green/red wire at the voltage regulator (or another wire in the #1 pin), I'm not sure how the charging system was working to begin with.

[nissanthanh]

Thanks SteveJ. Yeah I was bouncing and confused at the moment. Thanks for clearing that up.

Tried this morning to look for more connectors. Only found 1 4pin that was going to the fuel fume thing(last photo). Hopefully help you guys see what I'm seeing.

Driver's side wires. Hanging green wire

Driver's side connector that isn't plugging into anything. Black/white and green/red (could this be it?!?! why is it hanging over here...)

alternator shot

Firewall on passenger side.

Better open shot of passenger side wires.

Connectors on the right side of the regulator box(closer to front)

I messaged the other fella who had the same '75 missing green-red. Hopefully he responds asap too.

Thank you guys for all of your help. It's GREATLY appreciated.

Edited March 11, 2014 by nissanthanh

[SteveJ]

The plug I want you to find should be on the passenger side or maybe along the firewall. It will have the following wires: black/white, black, black/yellow and yellow (or yellow/black if the car was an automatic).

[Zed Head]

There are many threads out there about the mysterious missing wire, from about 1972 Z's up 1975 (now, in this thread). Nissan changed something in the cars but didn't change the documentation.

Shouldn't all of the wires needed be in the same spot as when he started? He had an external regulator connected. If he still has the connectors he could tape them back together for a visual and start over. Probably the best route since he's completely lost now. He really shouldn't be looking anywhere else in the engine bay except for where the external VR was.

Also, I haven't seen any signs of meter usage. Even a $5 Harbor Freight meter would be worth getting. You can't do these things right by wire color alone.

[nissanthanh]

I'll be skipping my workout today to take a meter to the vehicle and it's wires today. Sorry, trying to do too many things at once...

[Zed Head]

No offense intended.

It's always a good idea to check your work with a meter. Sometimes what you think is brown is actually red or blue is green. Or you miss the stripe on the back of the wire.

[Mark Maras]

Ditto that. I would include wiping the wires down with solvent & a rag will bring out the true colors. I've misidentified colors on wires before they were cleaned.