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1989 240SX SE
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Discussion Starter · #1 ·
I just want to preface by saying I promise I’ve done hours of painstaking research for the last 3 days trying to figure out the issue and how to solve this. I’ve literally stayed up til 4am with a headlamp on my head just messing with wiring, fuses, and grounding cables. I’ve used Google, I’ve searched on here and every other 240SX forum, I’ve watched many Youtube videos. I’ve taken my multimeter to the wires, grounding points, fuses, everything that’s obvious. There’s too much conflicting information.

Here’s the issue: My car was running fine before this whole ordeal (it had some bogging issues which I assume is a vacuum leak or bad gasket, idk yet). On the positive terminal post, there’s this little black connector, it literally hooks on to the positive terminal. It looks like a little black box with 2 plugs going into it - there’s 1 thicker wire that goes to a long connector, and then 2 thinner wires that go to a single stubby connector. That black box was corroded so bad, along with the positive terminal, that one day the car was getting no power. I’ve had experience with loose terminals before so I tried to just wiggle it on better and tighten the bolt. Bolt broke right off, so much rust and corrosion.

Pics:
Hand Finger Wood Thumb Gas

Finger Gas Jewellery Nickel Auto part


Because it was so messed up, the car wasn’t getting any power anywhere. No cranking, no lights, no clock on the gauge. The AGM battery is brand spanking new so that’s definitely not the issue. So I decided to cut off the positive terminal and splice on a new one, but I had to also cut off that black box because of all the corrosion and gunk in the plugs.

There were no other major electrical issues before I cut it off and put on new terminal posts. I didn’t tamper with anything other than the end of the positive cable, the wires connected to this black box, and then I also replaced the negative cable - hooked it up exactly as it’s supposed to go, made sure the grounding point was clean bare metal, I literally didn’t touch anything else.

Here’s my current wire setup:
Rock-climbing equipment Carabiner Electrical wiring Gas Tool


I’ve cut, stripped, crimped, and redone this setup about 3 times now. I decided to leave it at this to separate the wires because initially I just put them all into a single ring terminal. But none of these setups work. I’ve tried putting the ring terminals onto different positions on the positive terminal, I’ve even tried putting it onto a 100amp fuseblock that connected to the positive terminal. Nothing.

The reason I did it all this way is because I read many times that people cut off that black box with no issues, saying that they did exactly what I did and everything worked fine… But to be fair, those statements were referring to other Nissans because there is almost no information on this thing when it comes to the 240.

I’m hoping that someone finds the issue obvious because I don’t. I’ve taken my multimeter and tested the wires, the battery, the fuses, everything… I have absolutely no clue why cutting off that black box completely killed power to the whole car. It doesn’t even appear to have a fuse in it, and it’s straight up just connecting the wires to the positive terminal… This makes no sense to me.

Please help me, I need guidance, wisdom, ideas, anything. Heck, if someone can even just send me a new black box with the connectors (with some slack on the wires so I can splice it on) I’ll pay for it. I just want this car to run again.
 

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1989 240SX SE
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12 Posts
Discussion Starter · #3 ·
Welcome

Let's start with your car details.
What year, engine, auto or 5 speed

Any modifications? Like was it an auto car that you swapped to manual?
Hey, it’s a 1989 240SX SE auto KA24E SOHC with only a few mods but nothing electrical/wiring related. It has a power sunroof conversion done by ASC but that’s all I can think of.
 

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Hey, it’s a 1989 240SX SE auto KA24E SOHC with only a few mods but nothing electrical/wiring related. It has a power sunroof conversion done by ASC but that’s all I can think of.
You're probably going to want to see if you can find that cable on eBay or something. I almost changed the positive wire on my 96 till I saw how much its split and connected to. Not sure if that would help but it might and could be a start.
 

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1989 240SX SE
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Discussion Starter · #5 ·
You're probably going to want to see if you can find that cable on eBay or something. I almost changed the positive wire on my 96 till I saw how much its split and connected to. Not sure if that would help but it might and could be a start.
I’ve been trying but there’s 2 issues… I don’t even know what the wires are called or where they exactly go to so I don’t know if the connectors are the same. The other issue is that I can’t find the little black box anywhere - not on Ebay, FB marketplace, or any other marketplace really. I wish there were a junkyard near me with 240s but there isn’t a single 240 being parted out anywhere near me. I’ve been keeping an eye out and asking around but no luck.

The only info I know is that the positive cable and black box are connected to the lower harness, but I don’t want to pay $100+ just for a little connector.

My current gameplan is I’m gonna try splicing on fusible link wire to the end, replacing the alternator fuse, and then report back with progress.
 

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I’ve been trying but there’s 2 issues… I don’t even know what the wires are called or where they exactly go to so I don’t know if the connectors are the same. The other issue is that I can’t find the little black box anywhere - not on Ebay, FB marketplace, or any other marketplace really. I wish there were a junkyard near me with 240s but there isn’t a single 240 being parted out anywhere near me. I’ve been keeping an eye out and asking around but no luck.

The only info I know is that the positive cable and black box are connected to the lower harness, but I don’t want to pay $100+ just for a little connector.

My current gameplan is I’m gonna try splicing on fusible link wire to the end, replacing the alternator fuse, and then report back with progress.
You can try this site I got a battery bracket I couldn’t find. They have some of the oem stuff and they might have what you’re looking for.
Good luck hope this helps
 

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1989 240SX SE
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Discussion Starter · #7 ·
You can try this site I got a battery bracket I couldn’t find. They have some of the oem stuff and they might have what you’re looking for.
Good luck hope this helps
Hey, I appreciate you dropping the resource! I couldn’t find what I needed but I’ll definitely check it out again in the future.

Also, update… New alt fuse didnt do anything. Anyone please feel free to help guide me in the right direction because I feel so lost. Tonight I’m gonna try and trace the wires back as best as I can, but 2 of them are mounted into the fuse box and the other (larger/thicker) wire just goes to the starter, but it looks fine. Plus the starter isn’t the issue anyway, the issue is that the car gets no power at all - not to lights, not to the gauge cluster/clock, to the ECU… nothing. Wish me luck. I’ll be sure to come back with news, regardless of good or bad
 

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It really sounds like there's a ground either not hooked up or one that has corroded through.

I'd definitely grab the FSM for an 89 or a 90

You're gonna need to grab the schematics that are in the electrical or wiring sections and go from there.

I'm not familiar with the little black box but the theory is that it all is just hooked up to your battery so it doesn't matter. What you did is alright. As long as you are making good contact from your wires to the crimped contacts, you are fine. And I mean raw copper to bare metal on the terminal. The only other thing I could think of is if there is some wire that was accidentally cut off underneath the protective wire sheathing that didn't get connected back to the positive terminal.

So what I would do

Get a multimeter on your battery, verify 12V or more.

Get a multimeter on all your grounds and verify continuity from whatever ground point to the negative post on the battery.

Verify continuity from the positive battery terminal to the fusebox in the engine bay. There are certain places that get 12V and then it gets distributed.
Sounds stupid but on my truck, I had no power to anything. Ended up being that the main positive power (+12V) wire coming from the battery was pinched between my engine mount and frame. Good job GM on routing the wire through there. Once it was freed up from there, everything worked.


I felt like an idiot because I had schematics printed out and I was verifying continuity and shit on my ignition switch when I should have started from the source, aka the battery and worked my way towards the car.

Good luck, please be careful doing this because it will kill you if you get electrocuted.
 

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Discussion Starter · #9 ·
It really sounds like there's a ground either not hooked up or one that has corroded through.

I'd definitely grab the FSM for an 89 or a 90

You're gonna need to grab the schematics that are in the electrical or wiring sections and go from there.

I'm not familiar with the little black box but the theory is that it all is just hooked up to your battery so it doesn't matter. What you did is alright. As long as you are making good contact from your wires to the crimped contacts, you are fine. And I mean raw copper to bare metal on the terminal. The only other thing I could think of is if there is some wire that was accidentally cut off underneath the protective wire sheathing that didn't get connected back to the positive terminal.

So what I would do

Get a multimeter on your battery, verify 12V or more.

Get a multimeter on all your grounds and verify continuity from whatever ground point to the negative post on the battery.

Verify continuity from the positive battery terminal to the fusebox in the engine bay. There are certain places that get 12V and then it gets distributed.
Sounds stupid but on my truck, I had no power to anything. Ended up being that the main positive power (+12V) wire coming from the battery was pinched between my engine mount and frame. Good job GM on routing the wire through there. Once it was freed up from there, everything worked.


I felt like an idiot because I had schematics printed out and I was verifying continuity and shit on my ignition switch when I should have started from the source, aka the battery and worked my way towards the car.

Good luck, please be careful doing this because it will kill you if you get electrocuted.
Thank you so much for the wisdom. I checked like you said and I noticed something odd about my battery… I have a yellowtop Optima AGM battery. It’s brand spanking new, I bought it about 2 months ago.

I must have been on the ohm setting before because it’s reading about 12 ohms, but on the voltage setting it’s displaying 0. I thought maybe I wasn’t doing it right so I kept trying and no matter what I do, it says 0 volts.

Tested my multimeter on my mom’s car battery and it was reading correctly: 12.4 volts.

At the risk of sounding dumb… Do AGM batteries act the same as standard batteries in the sense they will display 12+ volts? I’m going to buy a cheap POS battery from Autozone in an hour and see if all this was just from a bad battery.
 

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I mean regardless of the composition of the battery, it's supposed to have +12V at the positive terminal, plain and simple. It could just be your battery.
If you have jumper cables, you can probably hook up to your moms car and check that way.

Remember, red goes to red, black goes to black. You should know instantly if it's the battery.

To answer your questions, yes AGM batteries should have 12V at the positive terminal ready to go.

I wouldn't hook up an ohmmeter to the battery.
 

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Discussion Starter · #11 ·
I mean regardless of the composition of the battery, it's supposed to have +12V at the positive terminal, plain and simple. It could just be your battery.
If you have jumper cables, you can probably hook up to your moms car and check that way.

Remember, red goes to red, black goes to black. You should know instantly if it's the battery.

To answer your questions, yes AGM batteries should have 12V at the positive terminal ready to go.

I wouldn't hook up an ohmmeter to the battery.
Final update on this.

I checked the voltage of my AGM battery again just to make sure everything is as it seems. Again, 0 volts. I don’t know how a 2 month old battery got to 0 volts, but oh well… Went to Autozone and pulled the trigger on a new battery. I’m keeping the AGM for now while I figure out warranty information.

Anyway, I installed the new battery and bam, instant power, heard the chime, and I was simultaneously furious and relieved. Somehow the battery went bad at the exact same time that I cut off that little black junction box… From there, it played the role of red herring.

So for anyone in the future who stumbles upon this, no - that black box connector on the positive terminal isn’t essential and as far as I can tell it doesn’t do anything, it doesn’t even have a fuse in it nor does it have fusible link wiring. You can crimp/solder the 3 wires into a single ring terminal and just bolt it onto the positive terminal (the same way I have it setup in that one picture above).

PS. Always double check the battery first before diving into electrical issues.
 

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Final update on this.

I checked the voltage of my AGM battery again just to make sure everything is as it seems. Again, 0 volts. I don’t know how a 2 month old battery got to 0 volts, but oh well… Went to Autozone and pulled the trigger on a new battery. I’m keeping the AGM for now while I figure out warranty information.

Anyway, I installed the new battery and bam, instant power, heard the chime, and I was simultaneously furious and relieved. Somehow the battery went bad at the exact same time that I cut off that little black junction box… From there, it played the role of red herring.

So for anyone in the future who stumbles upon this, no - that black box connector on the positive terminal isn’t essential and as far as I can tell it doesn’t do anything, it doesn’t even have a fuse in it nor does it have fusible link wiring. You can crimp/solder the 3 wires into a single ring terminal and just bolt it onto the positive terminal (the same way I have it setup in that one picture above).

PS. Always double check the battery first before diving into electrical issues.
Glad you finally got it man. Time to drive that thing like a mad man haha
 
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