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Bought a 1972 LP521

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Alright so I picked up this 1972 LP521 pickup a month ago. The previous owner said he translplanted a 2.0 nissan motor in it from a later datsun pickup. He also said the owner before him rewired everything. Well today i was trying to figure out all the wiring and it looks like things were bypassed in alot of places, old wires were spiced into new wires, larger guage wires went into smaller gauge wires. IT IS A NIGHTMARE!!!I want to rewire everything right, where can i find the right wiring diagrams for this truck and where could i buy a wiring harness for this thing?I will have pictures up later in the day.

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Look at what doesnt work first.

Even if he rewired .it was running one time correct?


well it runs great right now, its just my lights work whenever they want, i found a few fried wires, there are too many wires under the dash to sort out what is what, it has the original fuse box and some other fuse box that was from something else wired into the system.

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You cannot go to the Nissan dealer and buy a new harness, and the truck originally had three.

there was a harness for the engine compartment, one inside the cab, and one for the rear frame.

Originally there were six fuses for everything. The fuse holder gets corrosion on it over the years, and it gets hot. Then the spring clips holding the fuses get weak, they make a poorer connection, heat up more, and things keep getting worse.

A temporary fix is to polish the fuse contacts, and pinch them closer to hold the fuses more securely.

You can find a lot of information here:



Here is a brief description on the light circuit. There are two fuses for the lights, one for the headlights, and another for the smaller lights, Parking, tail, side marker, dash. Power comes from the battery, directly to the fuse box, and after the two fuses, goes into the cab. There is a bunch of harness connectors behind and above the glove box, and then the power goes to the light switch. After the light switch, power then goes back to the glove box connectors, and back into the engine room harness, and the rear frame harness. Headlight power goes to a relay, by the battery, and then out to the headlights. After the headlights, power travels back to a ground, and they are grounded by one of the screws holding the voltage regulator in place.

It is a fourty year old truck. Any of the connections could be weak, and need cleaning, and do not forget to check and clean the grounds.

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