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What battery to run


boxboy

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Didn't you see my wire color post before about three posts back?

 

Sure I saw it, but my wires coming out of the alternator don't match up. I don't have a real Yellow wire coming out of the alternator. I have a Black with white tracer and a kind of "yellowed" white wire that come from the brushes. A white with red tracer that goes internally to the "BATT" post and a white with green tracer that goes somewhere else. Anyone have any idea how this correlates to the B, Y, WB, W wires coming from the harness?

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Sure. The alternators have different wiring depending on year and model, but all 4-wire units are wired the same, regardless of the color.

 

As long as you haven't modified the wiring on the alternator, they all connect to the same wiring harness that goes into the voltage regulator.

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It correlates like this, as the connector will only fit one way:

 

_======_

| WB B |

| W Y |

--------

 

It should be marked on the regulator what these are for:

Y - Field

W - Alternator

E - Earth (ground)

WB - Nuetral

 

If your alternator has a blown diode, it won't put out the full 25 or 30 amps. If it has a shorted diode, it will run your battery down.

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My harness is stock, so I have B, Y, WB and W. I am assuming it matters where each wire from the alt. go, but like I explained previously, the colors don't match up like your original post. I am lost. When I hooked it up like I believe it was before my problem, it overcharged. I know the connector only fits one way, I just can't be positive I didn't get things out of order when I put new spades on the wires.

 

I also looked and I have an aftermarket VR and the wires don't have the same color code there either.

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It correlates like this, as the connector will only fit one way:

 

_======_

| WB B |

| W Y |

--------

 

It should be marked on the regulator what these are for:

Y - Field

W - Alternator

E - Earth (ground)

WB - Nuetral

 

If your alternator has a blown diode, it won't put out the full 25 or 30 amps. If it has a shorted diode, it will run your battery down.

 

Sorry, my regulator has no markings on it whatsoever. Just a six wire connector and a sealed black plastic box.

 

I must reiterate the obvious by now. I know nothing about electrical stuff. So, one by one, if I have two wires coming from the brushes on my alt. which would they correspond to? And a wire in the alt. going to the BATT post? And one that seems to be coming out of the stator?

 

I had a drain on the battery with the key off. Running I was getting decent readings, so I thought the alt. was good. I don't know what a diode is. :w00t:

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Got ya.

 

I never torn one down and traced the internal wires, but the factory wiring diagram shows the internal connections. It doesn't show how the brushes connect.

 

Maybe this will help:

 

The HARNESS wires should connect to:

W - A output terminal (diode assembly)

Y - Nuetral (stator common point)

WB - Field (brushes?)

B - Earth/ground

 

 

If you find the alternator or VR is bad, I would get rid of both and buy a $50 one-wire Hitachi. It's a straight bolt on with internal-regulator and more amps to boot. Cheaper than a replacement VR and same price as the old low-amp alternator.

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okay, with this description I am pretty confident that it was hooked up to the harness correctly. Now on to my next question. If I have a drain on the battery when the key is out of the ignition at 1.5 Amps more or less, and I have pulled each fuse in the truck one by one and had no change in that 1.5 Amp reading, then can I tell where my problem is? I am assuming that because of it overcharging that the VR is bad. Is that true?

 

Double checking, this is a J13 engine on a '68 520. Are you sure a the Hitachi you are recommending will bolt on?

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Yes, I'm sure.

 

If it is overcharging, it's either a bad voltage regulator or bad wiring (such as dirty or loose connection, or miswired or broken wire).

 

For the drain, unplug un-fused components until the drain stops. The alternator itself is the obvious suspect, but also try disconnecting just the VR. Track it down.

 

You can test the alternator drain using a Ohm-meter or Multi-tester. Put it on the high scale and connect Red wire to A terminal and Black wire to E terminal. (Disconnect the A wire and the 4-wire plug). Then reverse the leads. Only one direction should show a reading (more than zero). If a diode is shorted it will show a reading both directions. If the diodes are good then it will show a reading one direction and no reading the reverse direction.

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You seem to be saying 2 different things here. I have an overcharge situation. So, do I assume if my connections are good it is the VR? Will the VR cause a drain?

 

If my alternator is bad, can it still cause an overcharge situation?

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Yes, I'm saying different things in Reply to your different questions.

 

Yes, pretty much any electrical part can cause a drain. The VR can cause a drain. It also can regulate (or fail to regulate) the alternator output voltage.

 

No, an alternator cannot normally cause an overcharge condition. Because the Voltage Regulator will shut it off (if the Voltage Regulator is working correctly). But if the internal wiring is messed up it could cause on overcharge (for example if the Field is cross connected to A), it seems unlikely though -- never ran into it before.

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Yes, I'm saying different things in Reply to your different questions.

 

Yes, pretty much any electrical part can cause a drain. The VR can cause a drain. It also can regulate (or fail to regulate) the alternator output voltage.

 

No, an alternator cannot normally cause an overcharge condition. Because the Voltage Regulator will shut it off (if the Voltage Regulator is working correctly). But if the internal wiring is messed up it could cause on overcharge (for example if the Field is cross connected to A), it seems unlikely though -- never ran into it before.

 

Sorry, I don't mean to frustrate. Am I to assume the "A" is the "BATT" post on the alt.?

 

If I find either the alt. or the VR to be bad, is there a part # to tell them at Napa for the 1 wire alt.? Is it complicated to wire in?

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Sorry, we probably should have created a new topic. But "I need a new battery" usually means "how can I tell if my battery is bad, or if it's my charging system"?

 

The early Datsun alternators have two large terminals on back:

* E - for earth (ground)

* A - which connects to the fusible link, and thus to the positive battery cable

 

Later alternators were maked "BAT"

 

24376.jpg

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I have a working 4 wire alternator out of a 69 510 you can have if you come to seaside and get it. Bring a plastic bag its dirty. Its original and it works.

 

Or be a big baller, drive on out here with a new small 720 internally regulated alternator and we will install it in my car port, ill even do the IR alt bypass at your voltage regulator connector with two wires and four spades so you can retain your stock connector if you ever want to go back to externally regulated.

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I wimped out and had Napa test my alt. They said it is a good alt., but they couldn't guarantee that my drain wasn't coming from the alt.

 

I need to narrow it down to either the alt or the VR. So when I get home I will do some more hunting. Since the alt is off the truck now, I can hook up the battery POS and see if I have a drain. If not, wouldn't that confirm that it is either the VR or the ALT.? If I do have a drain with it off, then I suppose I need to start pulling non-fused wires off of say the starter etc. Correct?

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Okay, when I got home I spent some time testing. With no alt. hooked up at all there was no drain. I then hooked up the 4 wire, and still no drain. Then the grounds to the E terminal and no drain. Then I hooked up the BATT terminal and BINGO drain.

 

Then I unhooked the VR from the harness and no drain. I plugged that back in and took the wire from the alt to the starter off and there was no drain.

 

As for as testing the alt for drain, I think I am setting up the multitester wrong. I tried testing it on the bench with nothing attached to it, red to the BATT terminal and black to the E and my multimeter didn't read anything. Reversed them and it still didn't read anything. And by "anything" I mean it didn't register at all, not even 0.00. I am working with a cheap (but new!) Harbor Freight multitester.

 

Not sure where to go from here. It appears to my untrained eye that I either have a drain in the alt. or the VR. However, if my battery is over charging with a few rpms up to 16V, and Napa tested the alt and said its good, then I would presume it is the VR. Am I close?

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You are close. It sounds to me as if all is in the alternator.

 

What does this do?

* VR unplugged

* Alternator A/BAT terminal connected and E wire connected, 4-wire connector UNplugged

 

If it still drains, replace the alternator.

 

With this set up there is no drain.

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So it's a combination of Alternator + Voltage Regulator that is causing the drain. You don't need to check the alternator diodes, since there is no drain when it is connected from A/BAT to starter by itself.

 

That beings said, I think it is the regulator (or wiring). When you plug in the Voltage Regulator, it gets power through the 4-wire connector (via the A/BAT internally I believe). But the voltage regulator has two relays inside, and aren't supposed to draw the current until the IGN switch is turned on. The relay is like a set of points, and is probably stuck closed (burned like distributor points).

 

520_voltage_regulator.jpg

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Here are a couple of pics of my VR. Not anything like what you are showing here, so obviously not oe. There is no way to get in there and inspect as it is a sealed unit.

 

th_P1010213.jpg

th_P1010214.jpg

 

I might also add that earlier you mentioned a fusable link. Nowhere from my battery POS do I have a fusable link except to my headlight relays. There isn't any link between the starter and the alt either. Where is this fusable link supposed to be?

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So where do I go from here? Can I be relatively certain it is the regulator? If so, I checked at Napa and they can get me one for $32. You mentioned an alternative alt I could use that has an internal for $50. I am okay with swapping to upgrade if that is all the difference in cost is, provided that the swap is relatively simple. Could you give me a part number or a alt. to ask for to get a solid price? Can you tell me how complicated a swap would be?

 

I appreciate you sticking with me here as I learn.

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Well I was thinking 521 with L16 engine, for the 520 with J13 engine I'm not sure it bolts on the same. You might have to use a longer bolt and a spacer.

 

The wiring is easy. There's a two-pin connector. Connect one to the alternator A/BAT, and the other one to your wiring harness CHG lamp wire. See IR alternator into Datsun with 4-pin harnes

 

$75 NAPA part numbers Bosch AL242X, RAY 138130 or RAY 2138130

$50 at O'reilly's and Autozone

$37 at RockAuto.com Pure Energy 14231, Beck/Arnley 1860115,

For: 1980 Datsun 720 Pickup with L20B (USA 35A, not the 50A unit)

 

 

If yours has the three ears like this it will probably be a direct bolt-on:

21285.jpg

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