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New Member has alot of questions about an 85 720


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Hello all , newbie here and i have alot of questions for you folks.


   My son purchased a 85 Nissan 720. It is a single cab and 4 wheel drive. Someone in its past has jerry rigged the electrical system in this truck and done a pretty lousy job of it. The alternator is not charging the battery, we just bought a new one and it still doesnt work.

   They also have the headlights wired directly to the battery, they also installed a new radio that works sometimes but not often

  What we would like to do is rebuild the electrical system back to its original condition in order ot find out why the battery will not charge as well as return the headlights back to the original configuration. We have a chilton manual but i don't think it is showing us everything we need to know. 


Question 1.

  Where can we buy a wiring diagram ?


Question 2.

   Is there a source out there to buy a new wiring harness that is plug and play ?


Question 3.

  Does anyone have any pics of what the connection at the hoy side of the battery post should look like ? This truck has been butchered and they have a lot of wires coming straight to the battery.


Thanks in Advance


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Welcome to Ratsun.


All of the electrical power from the battery has to go through fusible links to protect the wires in the way to the fuse box. The positive battery terminal should have three, two Green and a Black. One Green goes to the ignition switch and then to the fuse box for things turned on and off by the key. The other Green powers the fuses for the head lamps. The Black one powers the fuses for things like the horn, brake lights etc that work without the key. The alternator is also on the Black fusible link.


Probably if you replace the needed fusible links the charge will work.

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If there's a lot of things hard wired to the battery they most likely had problems with relays. My fuel pump is hard wired because of the relays going bonkers, but I kept it in the ignition so it comes on with the key. If it's that bad, most junk yard 720's will have a harness that is usable. A new harness will cost you some coin, you could get a junkyard one for cheap.

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The fusible links have their own connectors and just plug in. It's a process of elimination... fix one thing move on to another. At some point, if really bad, it may be easier to swap the harness. Usually previous owners don't know why something does not work, they just 'make it work' as easy as they can.

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Thanks guys, we will swap out the fusible links. I dont want to Jerry rig this , its the first vehicle my son has owned that can actually be worked on so i want him to learn how to trouble shoot problems then fix them but i want to start out with something that is remotely like it is supposed to be.

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Radio problem may be as simple as a bad ground. I. Many aftermarket radios need a direct ground added in, in addition or instead of the factory harness ground. 85 would have had full radio wiring installed, so they shouldn't have needed to add anything. That being said, it's quite possible they cut factory connector out and hard wired the radio, which could also be the source of the radio issues.


Headlights, the most common issues would be the switch on the column and relay. Start by checking out those. .

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