Voltage Regulator Question

[SteveJ]

Bob, the strange thing is that Alex says that the black wire on the VR is going to pin #2. That should be the A wire to the battery. Even if the ground wire coming from the harness has been compromised (which there is always a possibility of that), it wouldn't account for the fact that the wires aren't lining up properly between the VR and engine bay harness.

[503Alex]

Really appreciate all of the help. I think an IR alternator is a good choice.

Bob, the strange thing is that Alex says that the black wire on the VR is going to pin #2. That should be the A wire to the battery. Even if the ground wire coming from the harness has been compromised (which there is always a possibility of that), it wouldn't account for the fact that the wires aren't lining up properly between the VR and engine bay harness.

I agree, it definitely seems like the black/white is the intended ground wire in the wrong slot. I just emailed BD with this picture to see if it's possibly wired wrong.

[SteveJ]

Another alternative is to take a chance with another VR. Rockauto has some wholesaler closeout ones pretty cheap.

[FastWoman]

Between the VR being wired wrongly to the plug and your car being wired wrongly, I'd place my bets on the car. After all, the PO had snipped off that black wire. That's not a proper fix and doesn't give me much confidence in anything else. I bet if you traced out the wiring from the VR connector, you'd find where it's spliced incorrectly into the wiring harness somewhere.

I don't see any reason to go to the IR alternator. It shouldn't be too hard a job to trace out the wiring between the VR and the alternator and find where the PO had miswired it. It should be easy to fix your VR, just by soldering back the wire that burnt away.

[Zed Head]

I overlooked the part about Pin 2 being the black wire on the harness plug. I just looked at both FSMs, 76 and 77, and they both show Pin 4 as black/ground. Pin 2 should be power from the alternator, a white wire.

I have attached a drawing from the 1977 FSM (Page BE-22) of the regulator side of the plug, just to confirm the wire colors, plus it shows where they come from. A for Alt, L for Lamp, E for Earth, Ig for switched power. I thnk that F and N come from the T plug on the Alt. It is upside down compared to Steve's Post #2 drawing.

You can see that it matches the 1976 wiring diagram.. L signifies a blue wire in the drawing, so you can see that they don't match wire colors across the plug for every wire. Blue in the harness goes to W/R on the regulator for example.

There is definitely something odd if your car's harness has a black wire at the Pin 2 position.

Any chance you could take a picture of this odd connector?

If you decide to go with the internally regulated alternator, be aware that the yellow wire also powers the brake light warning switch circuit. Your battery will slowly drain if you don't cut it, and wire it to a switched source.

Edit - Forgot to say that I already converted to an IR alternator so can't compare plugs.

Edited February 17, 2011 by Zed Head

[Zed Head]

Really appreciate all of the help. I think an IR alternator is a good choice.

I agree, it definitely seems like the black/white is the intended ground wire in the wrong slot. I just emailed BD with this picture to see if it's possibly wired wrong.

Black/white is switched power from the ignition switch. Black is the intended ground wire and should be opposite the bump on the plugs.

Maybe someone de-pinned your connector to clean it or put a new plug on and screwed up when they put it back together. FastWoman may have the right idea, get out the volt/ohm meter and see where those harness wires go. You'll need to know anyway even for an alternator swap.

[503Alex]

Between the VR being wired wrongly to the plug and your car being wired wrongly, I'd place my bets on the car. After all, the PO had snipped off that black wire. That's not a proper fix and doesn't give me much confidence in anything else. I bet if you traced out the wiring from the VR connector, you'd find where it's spliced incorrectly into the wiring harness somewhere.

I don't see any reason to go to the IR alternator. It shouldn't be too hard a job to trace out the wiring between the VR and the alternator and find where the PO had miswired it. It should be easy to fix your VR, just by soldering back the wire that burnt away.

I overlooked the part about Pin 2 being the black wire on the harness plug. I just looked at both FSMs, 76 and 77, and they both show Pin 4 as black/ground. Pin 2 should be power from the alternator, a white wire.

I have attached a drawing from the 1977 FSM (Page BE-22) of the regulator side of the plug, just to confirm the wire colors, plus it shows where they come from. A for Alt, L for Lamp, E for Earth, Ig for switched power. I thnk that F and N come from the T plug on the Alt. It is upside down compared to Steve's Post #2 drawing.

You can see that it matches the 1976 wiring diagram.. L signifies a blue wire in the drawing, so you can see that they don't match wire colors across the plug for every wire. Blue in the harness goes to W/R on the regulator for example.

There is definitely something odd if your car's harness has a black wire at the Pin 2 position.

Any chance you could take a picture of this odd connector?

If you decide to go with the internally regulated alternator, be aware that the yellow wire also powers the brake light warning switch circuit. Your battery will slowly drain if you don't cut it, and wire it to a switched source.

Edit - Forgot to say that I already converted to an IR alternator so can't compare plugs.

Black/white is switched power from the ignition switch. Black is the intended ground wire and should be opposite the bump on the plugs.

Maybe someone de-pinned your connector to clean it or put a new plug on and screwed up when they put it back together. FastWoman may have the right idea, get out the volt/ohm meter and see where those harness wires go. You'll need to know anyway even for an alternator swap.

I just checked out the harness connector yesterday again and pin #2 is the white/red wire, sorry for the confusion. I ended up cleaning the contacts on the alternator with some contact cleaner and traced the white/red wire to the alternator and everything is hooked up as intended.

[503Alex]

I'll break out the voltmeter and do some investigating.

[503Alex]

Interesting update to this, I sent BD a photo of the wiring on my regulator and told them part of the pin out on to confirm that it was right, and they ended up sending me out a new regulator. The new regulator is wired completely different.

[SteveJ]

They could have been given the wrong part by their supplier, or it could have been a QC problem at the manufacturer. Let us know how the new VR works for you.

[FastWoman]

Cool! I'll keep my fingers crossed for you.

Even considering the error, I think I'd still trace out the wiring between your alternator and new voltage regulator before plugging the thing in and firing up the engine. After all, the PO apparently encountered something weird/wrong too, as evidenced by the burnt/snipped wire.

[503Alex]

They could have been given the wrong part by their supplier, or it could have been a QC problem at the manufacturer. Let us know how the new VR works for you.

Cool! I'll keep my fingers crossed for you.

Even considering the error, I think I'd still trace out the wiring between your alternator and new voltage regulator before plugging the thing in and firing up the engine. After all, the PO apparently encountered something weird/wrong too, as evidenced by the burnt/snipped wire.

Thanks for the comments. The alternator ended up going out for one reason or another after all of this, so I never ended up using the new VR. I traced the wiring to look for issue and cleaned all of the grounds. I ended up getting an '82 ZX alternator and doing the swap. Everything works nicely now and the volt gauge is constant.