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Battery won't charge


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Hey everyone! I have a 68 520 and the previous owners did poor electrical work. Alternator works fine and replaced the regulator. They had the alternator wired incorrectly but as far as I know I have corrected all the wiring based on the diagrams. Battery still never charges. Just slowly drains over a few days especially if the lights are on. I'm thinking they miswired something I'm missing. Can anyone please tell me the wiring configuration going in to the voltage regulator!? Thanks

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Welcome

 

Here is the thing, who told you the alternator worked fine, the auto parts stores don't know shit anymore, it may work fine but it may not be an externally regulated alternator, we have run into this issue several times in the past, they sold an internally regulated alternator to sell something when the customer needed an externally regulated alternator.

It was not your fault and likely not the previous owners fault either if it is not the right alternator and it is sometimes hard to tell it is the wrong alternator, can you post a few photos of the alternator, mostly of any stickers and the back of the alternator?

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mak sure the alternator is getting 12volts from key at the T connector if it has one to energize the coils

 

I worked on a 520 a lont time ago there was a short somerwhere. I separated it at the fust box to deengage that circuit so the truck would run but never figured it out doing that day I had the truck.

 

see if the battery drains with the truck KEY OFF.

make sure the alt you have is good.

 

 

Edited by banzai510(hainz)
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Thanks for all the help everyone! It is definitely an external regulator alternator. And when on and running is producing 13.5 volts. It's just not getting to the battery. 

 

The truck had a short before and was draining while off but that was corrected and is now stready. Now the truck is draining .01 volts every 6-10 min when running. Which means I can drive the truck for a couple days before it won't start again.

 

13.3V is getting to the regulator but nothing is getting to the fuse box or battery. It simply slowly drains from 12.4. I've tried a duralast vr728 regulator and a vr121 as well since I've been trying to figure this out. Any ideas? Thanks

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I cannot even tell what type of alt it is half the time, another guy on here went thru this a while back and he said it definitely was an external regulated alternator, well it wasn't and he had taken it back to the auto parts store to have it tested, they didn't know what type it was either, it turned out to be internally regulated and it would not charge the battery wired that way.

Does the alternator look like this one on my alternator tester or is the alternator case smooth?

DSCN7868.JPG

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If you can find it marked LT this is an external regulated alternator.

 

If marked LR this is internal.

 

 

Ccse5W8.jpg

 

J13 25 amp alternator has the metal cover plate that extends to the very back of the case.  There were no internally regulated alternators until '78 when Nissan changed ALL Datsuns to them.

 

That cover has the brushes under it. I would take it out and check and clean them. The regulator sends power to the brushes which power the spinning electromagnet. If not making good contact or worn out it's possible that some residual magnetism in the rotor is making that small output. 

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Usually the data is on a foil label on the side of the case. This is my 100amp 2002 Altima alternator I put in my 710. Originally it was LT or external regulated and had to mod the car to accept the LR internal regulated one. Most '70s Datsuns were black lettering on silver and say something like LT135 for a 35 amp external regulated.

 

 

RHriTXo.jpg

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No there may not be anything on it. Maybe never was, maybe it fell off.

 

Clean or at least inspect the brushes under that cover. Doesn't cost a thing and may fix it and save a trip into town. Wouldn't that be something??

 

If you do replace keep the old one because it can be rebuilt at a later date and it's a better quality that the stuff that's re-manufactured these days.

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I've had an alternator test good at autozone, but was only putting out around 13.3v like yours. This isn't enough potential to properly maintain/charge a lead acid 12v battery. 13.5v is just barely float charge territory (eg trickle/maintain).

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Im not a 520 expert but would take it to a alternator shop to make sure it works.

Why? as you said the wire was fucked with so maybe the alt is good.

 

ck for a battery drain.

Charge up the battery and then hook up a test light between battery post and the battery cable. I will send a link.

if the test light comes on then disconnect the + output of the alt to make sure it not the alternator diodes shoring out then the drain will go away.

if good then pull fuses till the test light goes out. then you know you have a short on that circuit.

 

about 40sec in to the vid is how to do it!!!!!

 

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Just wanted to thank everyone for their help and give an update! Turns out when I took the alternator apart to clean I noticed the wires were jumbled inside!!! Earth and battery were switched so connections to the ground and fuse box were off. I was putting it back together with one of the diagrams from another thread here. You guys are Lifesavers !! Alternator is now producing 14.5v to the battery and lights and dash are actually lighting up strong now! Time to continue the restoration now that it's drivable. Thanks everyone! 

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  • 5 months later...

In N American cars the '78 and up Nissans were all internally regulated.

 

An internally regulated alternator put into a car with an external regulator won't turn off with the ignition. The regulator must be removed and the wiring modified. In addition the auto choke relay must be disconnected and another power source found.

 

Pksocalrealator..... told you they were crap quality.

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