83 datsun 720 wiring harness issues.

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calvinmfbates
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Joined: Sun Nov 29, 2015 12:15 pm
Car: 83 datsun 720

83 datsun 720 wiring harness issues.

Postby calvinmfbates » Sun Nov 29, 2015 7:10 pm

I picked up an '83 720 2wd 5spd with the 2.4l. It was made 11/82. It's got a few issues with most of the lights, horn, split and cut cables, relays, and still a few unknowns still. I could really use a decent wiring schematic for the truck if anyone could help me that would be awesome.


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waynosworld
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Re: 83 datsun 720 wiring harness issues.

Postby waynosworld » Mon Nov 30, 2015 9:36 pm

I wish I had saved one, but I only saved the 320 and 521 wiring diagrams to my computer.
The fusible links are very important, make sure them are good right at the start.

LowFlying720
Posts: 34
Joined: Fri Aug 15, 2014 10:24 pm
Car: 85/86 Nissan 720

Re: 83 datsun 720 wiring harness issues.

Postby LowFlying720 » Wed Dec 02, 2015 2:09 pm

where are the fusible links located at?

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waynosworld
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Re: 83 datsun 720 wiring harness issues.

Postby waynosworld » Wed Dec 02, 2015 11:44 pm

LowFlying720 wrote:where are the fusible links located at?
See the black connector mounted on the positive battery post and the black and red wires coming out of it, them are the fusible links.
Image
Here you can see the fusible links from the one plug on the battery post to the two plugs into the wiring harness that one of the fusible links got blown, so I wired a fuse into it.
Image
You need power to all of these fusible links, otherwise stuff don't work properly.
Here are the fusible links on my 1982 Datsun 720 diesel.
Image
I did forget to mention that when a fusible link blows, sometimes you cannot tell because the outside of the wire doesn't melt, so you have to feel the wire to see if it is soft inside(bad), or if you can feel the wire inside(good).
The only way to tell for sure is to disconnect the 2 plugs from the wiring harness leaving it plugged onto the battery, then using a volt meter, check for power on all 4 wires.
Also sometimes the big plug on the battery doesn't make a good connection either, you just have to test everything for power/12 volts.

LowFlying720
Posts: 34
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Car: 85/86 Nissan 720

Re: 83 datsun 720 wiring harness issues.

Postby LowFlying720 » Sun Dec 06, 2015 1:28 pm

Thanks I'll have a look at that later today after I sort out a couple more pressing issues.

LowFlying720
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Joined: Fri Aug 15, 2014 10:24 pm
Car: 85/86 Nissan 720

Re: 83 datsun 720 wiring harness issues.

Postby LowFlying720 » Sun Dec 20, 2015 3:48 am

OK I checked the fusible links and they all felt a little soft to me but they all checked out with power coming out of them. When I was testing them I even wiggled them around and twisted them to see if maybe they were broken but temporarily making contact but they were solid as a rock none of them even blinked.

When this started, at the same time that the alternator light came on, the turn signals and all of the gauges failed. The first time it happened it stayed off for about a day and then one time when I started it up everything was normal again but that only lasted for about 20 minutes and then it was off again and it's never come back again.

Is there a circuit or a relay that powers all those items that could have failed? I've checked all the fuses, none appear to be blown.

Rustytruckman
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Joined: Fri Dec 18, 2015 8:37 pm

Re: 83 datsun 720 wiring harness issues.

Postby Rustytruckman » Sun Dec 20, 2015 12:05 pm

It seems that I somehow logged in under the other account I made the other day because I was locked out of my waynosworld account, even though this is showing me as rustytruckman, sorry, I will try to remember to log in as waynosworld next time.

As long as you unplugged them from the rest of the harness when you tested them then they are good, they cannot be plugged in.
Grounds can be an issue also, have you pulled on or have you removed any grounds?
The next thing you should check are the wires going to the alternator, make sure they are all tight, disconnect the battery if you do anything more than wiggle on them, there is one that goes to the starter, make sure them are tight also, if the main wire to and from the alternator gets loose(bad connection), stuff starts going down hill fast, it will run, but only as long as the battery lasts
Another thing I would do is start checking all the fuses, I personally would just replace them, but if the headlights work, you might be able to skip them, anyway once them have been replaced I would start the truck, now if everything works, great, now while it is running, start wiggling each fuse and see if anything happens, I had the former owner of my 85 720 put a wire in the fuse block where the fuse was supposed to be to run his aftermarket stereo, when I bought the truck from him he removed it, now the fuse makes a connection less than half the time, I am always having to wiggle that fuse to get the radio to work, even when it quits while I am driving it.
LowFlying720 wrote:OK I checked the fusible links and they all felt a little soft to me but they all checked out with power coming out of them. When I was testing them I even wiggled them around and twisted them to see if maybe they were broken but temporarily making contact but they were solid as a rock none of them even blinked.

When this started, at the same time that the alternator light came on, the turn signals and all of the gauges failed. The first time it happened it stayed off for about a day and then one time when I started it up everything was normal again but that only lasted for about 20 minutes and then it was off again and it's never come back again.

Is there a circuit or a relay that powers all those items that could have failed? I've checked all the fuses, none appear to be blown.

LowFlying720
Posts: 34
Joined: Fri Aug 15, 2014 10:24 pm
Car: 85/86 Nissan 720

Re: 83 datsun 720 wiring harness issues.

Postby LowFlying720 » Wed Dec 23, 2015 3:43 am

Ok problem solved. It was a bad fuse. I had checked all the fuses a couple of times. But I had done it by pulling them out and looking at them. The one that was bad looked good, no break, no discoloration, but it's as dead as a door nail. I pulled out each fuse and replaced it one at a time with a new one and viola everything came back.The weird thing is that only one of the things that was failed and came back was listed as running through that fuse.

Anyway thanks for your help take care

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waynosworld
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Re: 83 datsun 720 wiring harness issues.

Postby waynosworld » Wed Dec 23, 2015 12:10 pm

That's great!
You cannot trust the fuses by looking at them when things get weird, you just have to replace them sometimes.

The thing about the fusible links is that they will show dead while the engine is turned off and unplugged from the harness, but for some reason while the engine is running and they are connected, they will show as having power after the fusible link, that is why I say to unplug them from the harness when testing them, I think that it has something to do with the alternator and power back feeding thru the harness somehow, things work when it is running, and they don't work when it is not running.

Sharp720
Posts: 2
Joined: Sat Feb 13, 2016 11:17 am
Car: 1985/1986 Nissan 720

Re: 83 datsun 720 wiring harness issues.

Postby Sharp720 » Sat Feb 13, 2016 11:25 am

I am having a problem with my fuseable links I bought the car and they were rigged up. The RL and RY along with the WG and WR were not connected to anything. My wiring diagram shows the Reds going to the low pressure switch and I do not see the whites.

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waynosworld
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Re: 83 datsun 720 wiring harness issues.

Postby waynosworld » Sun Feb 14, 2016 12:13 am

Sharp720 wrote:I am having a problem with my fuseable links I bought the car and they were rigged up. The RL and RY along with the WG and WR were not connected to anything. My wiring diagram shows the Reds going to the low pressure switch and I do not see the whites.

I am not sure what you are talking about, but I don't have a 85/86 wiring harness diagram on my computer.
I don't even show a WG wire in the 82 diagram, and the WR wire goes from the fuse block to the ign switch.
Can you be more detailed, where are the WG/WR wires at, in the engine compartment?, near battery?, near fuse block?, I have an 85 720 I can look at if I know where to look.

Sharp720
Posts: 2
Joined: Sat Feb 13, 2016 11:17 am
Car: 1985/1986 Nissan 720

Re: 83 datsun 720 wiring harness issues.

Postby Sharp720 » Mon Feb 15, 2016 9:19 am

If you look in the middle picture you can see two red wires with a connecter on the end were do they go?all wires are near the battery. You can also see both the WR and WG wires connected to the battery.
waynosworld wrote:
LowFlying720 wrote:where are the fusible links located at?
See the black connector mounted on the positive battery post and the black and red wires coming out of it, them are the fusible links.
Image
Here you can see the fusible links from the one plug on the battery post to the two plugs into the wiring harness that one of the fusible links got blown, so I wired a fuse into it.
Image
You need power to all of these fusible links, otherwise stuff don't work properly.
Here are the fusible links on my 1982 Datsun 720 diesel.
Image
I did forget to mention that when a fusible link blows, sometimes you cannot tell because the outside of the wire doesn't melt, so you have to feel the wire to see if it is soft inside(bad), or if you can feel the wire inside(good).
The only way to tell for sure is to disconnect the 2 plugs from the wiring harness leaving it plugged onto the battery, then using a volt meter, check for power on all 4 wires.
Also sometimes the big plug on the battery doesn't make a good connection either, you just have to test everything for power/12 volts.

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waynosworld
Posts: 232
Joined: Mon Aug 24, 2015 11:10 pm

Re: 83 datsun 720 wiring harness issues.

Postby waynosworld » Mon Feb 15, 2016 5:10 pm

I don't have a 1985 wiring diagram, and I just searched for one online without success.
You need to find a 1985 wiring diagram, I only have a 1982 diesel wiring diagram which does't have the W/R and W/G wires.

MunkeeKnuts
Posts: 4
Joined: Sun Jan 28, 2018 4:11 pm
Car: 1985 Nissan 720 pickup longbed

Re: 83 datsun 720 wiring harness issues.

Postby MunkeeKnuts » Tue Mar 27, 2018 3:08 pm

Hi all - I'm looking at your posts and realize I need to find a replacement for my Fusible Link. My Fusible link is identical and has a copper clip onto the battery post, but that part isn't made anymore for my 1985 Nissan 720. Any ideas on replacement for this Fusible Link Clip?


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