Datsun Roadster Forum-311s.org

Not sure if my voltage regulator is working but I’m not entirely sure how to test it. What I do know is the bottom fuse isn’t work which is responsible for fuel gauge/temp gauge/and blinkers. If my suspicion is correct the ignition wire that feeds into the bottom fuse is the problem. The reason why I believe this is because when I detach the other side of the bottom fuse and hold it to another fuse, then I get power to blinkers and gauges. Below I’ve attached a couple photos and it seems the only wire that is getting any sort of reading is the white wire that is circled. No idea if any of this is related but would appreciate some help. Also I did make sure to check that everything is grounded correctly.

The white wire should always have +12 measured to chassis ground, the black wire/white stripe should have +12 when the key is "on/run". Plain black wire is ground. The yellow and white/black stripe connect to the alternator internal connections. (Neutral and field). The charging system should work independent of all fuses. Those terminals do not look too great.

I am at a complete loss as to why the black and white stripe wire is not putting out 12volts while the engine is running. I will try to clean all the connections and reports back.

Best to take the alt up to the part store to test ,unless fairly new
Crack the voltage reg cover , the 2 coils one brake l/ charge lite and the charge coil. up on the contacts is charging full , the coil builds magmatism and pulls the contacts off vibrating on and off as you start iand begins to run t it should be full charge
Check ohms on those wires to the alt and at the contacts
Yes wiring looks a mess
try a jumper cable neg post to alt mount too

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kennyele11 wrote: Mon Dec 06, 2021 8:01 pm I am at a complete loss as to why the black and white stripe wire is not putting out 12volts while the engine is running. I will try to clean all the connections and reports back.

Well if the black wire/white stripe is dead while the engine is running, that is likely a significant part of the problem. That wire activates the regulator, so if it is dead, the regulator thinks the car is off, charging is disabled.

There could obviously be other issues, but the system is not going to function until the black/white wire is powered up.

Hope that helps! J

Ps. If you need to test the alternator, that can be done without removing it.

Update: ran a wire from the black/white ignition coil wire and spliced it into where the black/white wire meets the voltage regulator and now the bottom fuse is working again and I have blinkers and gauges. Will check if system is charging tomorrow.

Sounds like you have a connection problem at the fuse box(very common) and possibly a connector/harness problem.

You are on the right track though, that black/white wire should always have power if the key is "on" or running. If I recall-refer to the wiring diagrams, the B/W should be "hardwired" independent of any fuses, but it does go through at least one connector.

For the B/W-to-regulator wire specifically, it might simply be the connector under the dash where the engine harness meets the dash harness (just inside the firewall next to the clutch master cylinder) , There is a connection there, and from there the B/W wire routes from the drivers side all the way around the engine bay to the regulator.

hope that helps!

Okay so I tested to see if the battery is being charged now and it’s charging at 15.5-16 volts. Could the voltage regulator be bad? Is their an adjust I can make? Do I need a new alternator? Pretty sure I have the stock alternator.

Good job, the alternator is definitely working ok if there is that much voltage present. If it doesn’t have any mechanical
issues, it is probably fine.

The regulator works by turning on/off the alternator very rapidly (controlling duty cycle in electrical terms).

The regulator is not super precise so it is not unusual to see voltages over 15 or 16.

Is your ammeter working? Ideally it should run just over the mid point unless the battery is partially discharged.

Be sure to clean ALL the regulator connections perfectly, and the 4-pin connector at the alternator, if there are any poor connections, the regulator can’t function properly.

We have regulators in stock if you want to try a new one, but clean all those connections really well first.

The ammeter is running just a little over the mid point, will try cleaning all the connections, if that doesn’t work I will likely purchase a regulator from you.

I think you are probably ok as-is to be honest. If you add more load (headlights, wiper, heater motor etc) it will probably pull more to the center. You are certainly welcome to try a new one, but it sounds like yours is doing pretty well If it was charging up at 18 or 20V all the time, I’d say swap it.

kennyele11 wrote: Tue Dec 07, 2021 4:37 pm Okay so I tested to see if the battery is being charged now and it’s charging at 15.5-16 volts. Could the voltage regulator be bad? Is their an adjust I can make? Do I need a new alternator? Pretty sure I have the stock alternator.

Theres an adjustment but dont try it its for the manu .special tools
Mostly its a bit oxydized in the contacts or the weak wiring ,like you showed , and if so a new one likely will be off too. 16 volts range will work to blow your delicate lite bulbs esp in heat and the batt. If long trips
whats is reading with high beams and blower on , t signals if amps are low it gives higher volts
Some how, I thinking you were talking wb wire but twas bw