What battery to run

[ggzilla]

here are the dimensions (same as late 510, and 620 small alternator)

• Distance between lower mounting ears: 80mm
  
• Distance between Adjustment bolt and mount bolt: 156mm
  
• Fan belt center: 29mm from front bolt face
  
• Pulley diameter: 69mm
  

[boxboy]

And, what advantage will this give me over buying a VR from Napa and sticking with the orig. alt?

 

I am assuming more amps, but are there problems with the VR's now that make them a frequent problem? Will I have to fiddle with wiring the new VR, or is it just plug and play?

 

The wiring seems simple enough now that you have taught me what everything means. But I just spent $70 on a battery. For $18 more, what are the advantages?

[ggzilla]

For $35 the best choice may be just to replace the existing VR. That's what I would do rather than pay $75 to NAPA for a rebuilt alternator. Instead I bought the 1980 alternator from Pick-n-Pull for $12.50 on a half-off sale day. It came with a warranty.

 

The advantage of just replacing the VR:

* less hassle. Buy it and plug it in. Test it for proper output (e.g. 14 volts)

 

Here's the advantage of the newer alternator:

* Those aftermarket VRs don't seem very reliable. Versus: never seen an internal regulator go bad

* It is 35A, which is enough for heaters, wipers and headlights. 25A is not enough, and 30A is marginal -- if you have to drive for hours in the rain at night, your battery can slowly go flat.

* The internal VR is built-in to the alternator, so there is no installing.

* Not only do you get a new regulator, but you also get a rebuilt alternator (they are one unit)

But the downside is a little fiddling with wiring, unbolting and rebolting and re-tensioning the fan belt

 

Why buy new parts? Peace of mind? That can be worth it. You have to decide.

[boxboy]

Okay, so I bit the bullet and bought an alternator from O'reilly's. $57. I really don't want to replace the VR and find out 6 months or a year from now that my alt. needs new brushes or that the internal wiring has gone bad or what have you. Plus if I misdiagnosed, I will be replacing both parts! I asked the parts guy what he would recommend and he said what I was doing for him was a no brainer. Said the VRs suck and are always going bad. So, this saga may continue as I try to wire up my new alt. Parts guy has had Datsuns and said he wouldn't bother with a fusable link with only a 35 amp alt. Do you agree? I do already have a 10g wire.

[ggzilla]

Parts guy has had Datsuns and said he wouldn't bother with a fusable link with only a 35 amp alt. Do you agree? I do already have a 10g wire

Fusible Link protects from fire ... however it is like insurance. Few cars have caught fire from wiring problems. Yours has already gone more than 40 years without a Fusible Link! On the other hand, Datsun 720 had "only" 35A and they used two fusible links.

[DanielC]

A 10 Ga wire will pretty much carry 35 amps all day long.

 

I do not think I have never has a original Nissan (Datsun) voltage regulator go bad, but aftermarket ones are not as good.

 

A 521 does not have any fuseable links. On an 521 as it left the factory, the wire from the hot side of the Alternator went almost directly to the big terminal on the starter, a distance of about 6 inches. Not much chance of a short circuit there. There was also a thick wire from the positive battery terminal to the fuse box, a distance of about 9 inches.

 

If you do get an internal regulated alternator, you must still leave the big black wire that is connected to one of the mounting bolts for the voltage regulator to the inner fender. There should be two thick black wires there. One grounds the headlights, the other wire goes back to the alternator frame.

 

Make sure the grounds are good between engine and the frame of the truck, the cab, and the bed of the truck. Making sure these grounds are good will go a long way toward eliminating wacky electrical problems.

[boxboy]

I thought I would do a write up of this process. I took pictures along the way and I want to make sure I have done it right. Let me know if there are errors.

 

First, I took my old VR (Voltage Regulator) and cut all the wires off of the back and saved the 6 wire connector and spades with lengths of wire. Since you only need the Yellow, black with white stripe, white and white with red stripe, I pulled the remaining two wires out of the connector. Then I created jumper wires out of the W and Y wire. (you could just put in a jumper in the stock harness, but this looked cleaner to me, and it maintains the color coordination to cut down on confusion) and the WB and the WR wires. Then I took this jumpered connector and plugged it into the stock harness where the VR used to be. In addition, I screwed down the ground to the fender where the VR was previously mounted.

 

 

The next step was to take one of the "T" connectors off of the pigtail. In order to avoid more wiring work, I pushed the existing spades out of the connector. The I took the old 4 wire connector plastic from the old alternator and took all of its connections out. I pushed the new alt's Y and WB wires into the corresponding slots to the wiring harness 4 wire connector. All of this avoids any messing with the stock harness wires, and insures the next guy will know what goes where.

 

 

Then for mounting, I cut two 1-1/2 inch pieces of 1/2 inch galvanized pipe for spacers to use for mounting. I bought a 5" bolt 3/8" size and mounted the unit to the truck. If your bolt is any longer than 5" it will be a pain to fit because on the J engine you either hit the oil filter or the radiator with a longer bolt.

 

 

Then for the wiring. For some reason there is a ground to the fender from the original harness in addition to the one from the battery NEG cable. I hooked them both up to the E terminal on the back of the alt. Then I plugged the 10 gauge wire from the starter to the A/BATT post on the back of the alt and finally the pig tail with my modified 4 wire connector to the stock harness. Good news, no more battery drain!

 

 

If someone could look this over and let me know if it all looks good, I will brave turning the key. I have 12.5 V on the battery with the key off, and no drain.

[ggzilla]

Nice work.

 

I would connect the S wire to the BAT terminal on the back of the alternator. And then connect the L wire to the WR wire in your existing wiring harness. It's cleaner and relies less on the original wiring connections.

[boxboy]

Nice work.

 

I would connect the S wire to the BAT terminal on the back of the alternator. And then connect the L wire to the WR wire in your existing wiring harness. It's cleaner and relies less on the original wiring connections.

 

I debated. I didn't see where I had WR that I could tap into other than all the way over where the VR was. I didn't want to run all that wire.

 

Thanks again for all your help ggzilla. I hope this leads to many a trouble free mile.

[DanielC]

"For some reason there is a ground to the fender from the original harness in addition to the one from the battery NEG cable."

 

The headlights have a dedicated ground to the voltage regulator. The additional ground wire is for the smaller lights, the front park lights and turn signals are grounded to cab sheet metal. If the additional ground wire was missing, the parking lights will try to ground through cables between the engine and the cab.

[boxboy]

I have a mod for the headlights with two relays. (Orig was missing when i got the truck and wired directly) I put a ground direct from the relay to the fender. Does this mean I don't need the one from the harness?

[DanielC]

I do not know about exactly how a 520 headlight circuit was wired, stock.

I also do not understand how your truck has been changed. The ground from the relay directly to the fender may only be for the relay coil. I do not know.

 

I do know how a 521 headlight circuit was wired.

 

When you turn the headlight on, power is applied to a thick red wire with a yellow stripe. This wire comes from the dash board mounted headlight switch, and goes to both one side of the switch inside the relay, and the coil inside the relay. If this was a Bosch cube relay, power is applied to pin 30, and 86

 

The normally closed contacts in the relay then apply power to the thick red with a black stripe wire. In "Bosch" language, pin 87A

 

When you put the turn signal switch in high beam position, it grounds the coil of the headlight relay. (pin 85) When this happens, the relay switches to the normally open contacts (pin 87), and applies power to the thick red white with a white stripe.

 

After the power goes through the headlights, a black wire on the headlight harness goes back to the voltage regulator mounting.

[boxboy]

I am so depressed. I went out to test out my install this morning. Alt light came on with the key just like it is supposed to everything looked fine and the battery hadn't drained at all since last night. In fact it read 2 hundredths more. I started the truck and it took a while for the alt light to go out. In fact I had to rev the engine just a little. Then I went out to check if it was charging with the multimeter. At a fast idle it was reading 12.3 V and when I revved up to 2K it was reading 16V or just under! How is this possible? New rebuild alternator with I am assuming a new IR in it. Any clues?

[ggzilla]

It's a wiring issue. Does your CHG lamp come on with key ON engine OFF?

 

For the grounds, it is most important to ensure your truck has the essentials:

* Engine ground (battery Negative to engine block)

* Body ground (either battery negative to body or from engine block to body)

[ggzilla]

S to head of T (12V, either permanent, or through IGN)

L to stem of T (dash lamp wire of engine harness)

 

[DanielC]

This is how I tested an unknown IR alternator on my truck.

Bolted it on, put on belt

Hooked up the frame of the alternator back to the battery, and ground.

Hooked up the battery positive wire to the large positive terminal on the alternator.

Hooked up a test light to the "L" terminal of the alternator, and the other end of the test light to battery positive.

Hooked up a wire from the "S" terminal to battery positive. Leaving this wire hooked up permanently, without switching it will drain the battery.

 

Before you start the engine, the test light should be on. When the engine starts, the test light should go off almost immediately.

Rev the engine up. The voltage at the battery should be around 14 to 14.5 volts.

[ggzilla]

Leaving this wire hooked up permanently, without switching it will drain the battery.

Nissan wired it to BAT + (not IGN) on at least two models (both the 50A and 35A units), at least per the wiring diagrams. When I fitted them, I did similar to boxboy and used a Switched wire from the existing wiring harness.

[boxboy]

It's a wiring issue. Does your CHG lamp come on with key ON engine OFF?

 

For the grounds, it is most important to ensure your truck has the essentials:

* Engine ground (battery Negative to engine block)

* Body ground (either battery negative to body or from engine block to body)

 

I do have the IGN on with the key in and not with key off. It did take a while for it to go off when I started the truck, but once it had a little gas it went off.

 

My NEG battery cable is bolted to the engine with a small wire also going to the E on the alternator. The E also has a wire running to the fender through the orig. wiring harness (Body ground?). I noticed the other day when I was hooking up the alt. that I connected the fender ground first, before anything else and it began to draw battery. (I had the test light hooked up) Once I plugged in the BATT/A wire to the starter it quit.

 

Now I have the S (Yellow) going into the orig harness Y and then jumpered to the white harness wire as instructed. The L wire (WB) is connected to the WB harness wire and jumpered to the WR of the IGN light. Right so far? I know you suggest running the Yellow S wire to the A/BATT post, but the WB wire still has to go to the WR wire which is all the way over on the fender wall. So I just ran it through the stock harness rather than run an additional wire.

[ggzilla]

Check the voltage at the T-connector. Pull it out of the distributor and verify with key ON, you have 12V at both wires.

 

There is also the possibility that the new alternator is defective. Have O'reillys test it.

 

Sounds like your ground wires are adequate. Whether they have a good connection or not has yet to be tested.

[boxboy]

Check the voltage at the T-connector. Pull it out of the distributor and verify with key ON, you have 12V at both wires.

 

There is also the possibility that the new alternator is defective. Have O'reillys test it.

 

Sounds like your ground wires are adequate. Whether they have a good connection or not has yet to be tested.

 

Out of the distributor? You must mean alternator. So I am testing the Y wire S and the WB wire L?

 

Could I run a dummy ground from the alt frame to the fender to double check that ground?

[ggzilla]

Yes, i meant alternator. Test the T-connector at the very end. Make sure both have 12V with key to IGN/Run position.

 

Yes, run an extra ground wire, can't hurt. You can use Jumper cables even. Just make sure they are to bare, shiny metals. Not to a painted surface.

 

And think of the money you are saving. Most people pay the dealer $200 every month, and still have to take it in for repairs occasionally.

[boxboy]

Yes, i meant alternator. Test the T-connector at the very end. Make sure both have 12V with key to IGN/Run position.

 

Yes, run an extra ground wire, can't hurt. You can use Jumper cables even. Just make sure they are to bare, shiny metals. Not to a painted surface.

 

And think of the money you are saving. Most people pay the dealer $200 every month, and still have to take it in for repairs occasionally.

 

Ha :w00t: That is what I tell my wife when she complains about me spending too much time in the garage!

 

How am I to test the T connector terminals? Both leads to the same termal? One grounded and one to the terminal? I don't get it.

 

If this doesn't work I will take the alt in and have it tested. It would piss me off if I got another bum part. I have had this happen several times with parts, even when I pay extra for the "premium" brand. :sneaky:

[ggzilla]

That's why i never pay more for the premium parts. Sometimes they are better materials, but these days most are just warranty options (paying more for a longer warranty, but the part is exactly the same). The true premium brands are new (not rebuilt) OEM parts (Hitachi, etc as installed by Nissan).

 

To test for 12V: Put your VMM/Voltmeter/Multi-tester red lead to the wire to be tested. The black lead to the battery negative post. It should read the same as the battery voltage.

 

You can also use a test light, but it won't tell you if it is 12.5 or 12.1 volts. If lower than the battery voltage it would indicate a wiring problem (dirty connections).

[boxboy]

That's why i never pay more for the premium parts. Sometimes they are better materials, but these days most are just warranty options (paying more for a longer warranty, but the part is exactly the same). The true premium brands are new (not rebuilt) OEM parts (Hitachi, etc as installed by Nissan).

 

To test for 12V: Put your VMM/Voltmeter/Multi-tester red lead to the wire to be tested. The black lead to the battery negative post. It should read the same as the battery voltage.

 

You can also use a test light, but it won't tell you if it is 12.5 or 12.1 volts. If lower than the battery voltage it would indicate a wiring problem (dirty connections).

 

I can't get the test to work, so I must be doing it wrong. With the meter set to 20DCV, the key on and the testor red on the top of the T and the black on the battery NEG I get nothing. Same with the stem.

 

I took the Alt in to O'reilly's and they said it tests out at 14.6 V, so it is a "spot on alt" according to them.

[boxboy]

ggzilla, I want to try wiring it your way and see what happens. But it seems strange to me to take the S (Y) wire that comes out of the alt and attach it right back to the A/BATT post on the alt. Am I understanding that right? I tried just doing that and leaving the L (WB) wire running thru the harness to the connector and jumped to the IGN light (WR) wire. When I did that, the IGN light would not go on with the key. I am assuming that is really the same set up (all be it with old wire) that you are proposing. Am I right?