Big Electrical Problems, AC, Dashboard, Multiple Accessories (1986 300zx z31 N/A)

jacoLiz

Forum User
Hello, sorry if this is a bad post I am new to forums.

So, somehow I managed to make my first project car a 1986 300zx that runs and drives and could use some love. I have never really done much on a car besides a brake pad change and oil changes, so this is a really big hurdle for me. I have been struggling to find
information and maybe I just need a little guidance through this issue. I pretty much just have some cheap tools and an equally cheap multimeter. But, here is what's happening:

So far what doesn't work are the: Digital Air Control, Cigarette Lighter, Windshield Wipers, Wiper Fluid Sprayers, Horn, Compass and MPG gauges, and most of the digital dash (warning lights work so far, Power Supply repaired already, no luck there).

What does work are the: radio (aftermarket), speakers / the girl that speaks to me when the door is open, windows, most lights (interior and exterior; blinkers, brake lights, ect.), speakers, headlight motors, and most other electrical components that are needed to drive it.

So far I have checked:
New battery + Battery cable connections
All fuses in the fuse box behind the kick panel on driver side interior
Relays for horn and wipers with relays that are known to work (will probably just replace all soon)
Digital Dash Power Supply

What I plan to check soon:
Ground connections
Fusible Links (don't really know how yet but I know where they are)

I am just unsure what all to check next. Honestly my long term goal is to just get this car inspected and drive it around for fun (Louisiana moment) so I need things like speedo and Odometer. It's fun to take around the neighborhood and such but you can only go in circles so much before you want more. Any advice here would be helpful, and I appreciate any and all of it. I knew this would be a tough task when taking it on but I've already really fallen in love with this thing.
 

Rob Gaskin

Treasurer
Staff member
Site Administrator
Well I'm not familiar with Z31 electrics and even if I was diagnosing something remote from the car is difficult.

You have done a lot of the basic stuff so you seem to have a general understanding.

Is there only one fusebox, make sure?

Do you have a wiring diagram - if so you need to see what wiring is common to the circuits that aren't working (if at all).

Try tracing just one of the circuits (cigarette lighter ?) from battery to component and see if you can find the problem - if so you might discover a bigger issue like rodent chewing?

You just have to be very methodical and if necessary draw circuits separately to avoid confusion. I do that so I can focus on just a very specific area.
 

MCBladeRun

Club Member
Fusible Links (don't really know how yet but I know where they are)
Hi jacoLiz

If you know where the fusible links are, I'll run through a basic how-to on testing these:

You'll need to preform a "continuity" test using your multimeter. Hopefully you're familiar with your tester. I'm assuming here that you have a dial on the front with lots of different selections to choose from.

You'll want either the resistance in ohms, at any of the ranges (we're not interested in the actual resistance here, just if there's continuity) or you'll want the tone test (which is when you stick the 2x probes together, the tester makes a noise).

This next bits crucial to do the test correctly: you'll need to disconnect one end of the fuse link. This ensures you don't have a false-positive result, such as a separate circuit giving you a false reading.

Put the 2x probes on either end of the fuse link ends. If you've got a reading of zero, anything such as 32.6ohms for example, or even a tone from the tester = this means the fuse is ok and has not broken (or fused).

If however the tester doesn't make a tone noise, or says something similar to >2000ohms for example. It means there is no continuity and that the fuse has broken and warrants a replacement.

Sorry it's long winded. Reply on here if you need further explanation or DM me 👍
 

jacoLiz

Forum User
Well I'm not familiar with Z31 electrics and even if I was diagnosing something remote from the car is difficult.

You have done a lot of the basic stuff so you seem to have a general understanding.

Is there only one fusebox, make sure?

Do you have a wiring diagram - if so you need to see what wiring is common to the circuits that aren't working (if at all).

Try tracing just one of the circuits (cigarette lighter ?) from battery to component and see if you can find the problem - if so you might discover a bigger issue like rodent chewing?

You just have to be very methodical and if necessary draw circuits separately to avoid confusion. I do that so I can focus on just a very specific area.
I think there is only the one, that and the Relays / Fusible Links. Thank you for the advice!
I actually just got a service manual so hopefully it has a wiring diagram inside. I'm planning to try and get at the digital dash connections on my next day off to check if they are loose or bad, so while I'm at it I might try and retrace one of those wires if I get to it.
 

jacoLiz

Forum User
Hi jacoLiz

If you know where the fusible links are, I'll run through a basic how-to on testing these:

You'll need to preform a "continuity" test using your multimeter. Hopefully you're familiar with your tester. I'm assuming here that you have a dial on the front with lots of different selections to choose from.

You'll want either the resistance in ohms, at any of the ranges (we're not interested in the actual resistance here, just if there's continuity) or you'll want the tone test (which is when you stick the 2x probes together, the tester makes a noise).

This next bits crucial to do the test correctly: you'll need to disconnect one end of the fuse link. This ensures you don't have a false-positive result, such as a separate circuit giving you a false reading.

Put the 2x probes on either end of the fuse link ends. If you've got a reading of zero, anything such as 32.6ohms for example, or even a tone from the tester = this means the fuse is ok and has not broken (or fused).

If however the tester doesn't make a tone noise, or says something similar to >2000ohms for example. It means there is no continuity and that the fuse has broken and warrants a replacement.

Sorry it's long winded. Reply on here if you need further explanation or DM me 👍
Thank you, I will be putting this to the test hopefully Friday before work or on my next off days. I did something similar to this on the fuses on the inside of the car, so hopefully I can figure it out for the links. I'll post an update / edit on what I find and if any of them are blown.
 

mrM

Club Member
your model is usa or au spec and different from uk models in its digital dashboard but obviously some things are the same,i would check continuity of fuses as sometimes they look fine but sometimes are duff,obviously the relays in the box under the bonnet and also the relays in the drivers footwell above the fusebox as a start point
 

jacoLiz

Forum User
Hi jacoLiz

If you know where the fusible links are, I'll run through a basic how-to on testing these:

You'll need to preform a "continuity" test using your multimeter. Hopefully you're familiar with your tester. I'm assuming here that you have a dial on the front with lots of different selections to choose from.

You'll want either the resistance in ohms, at any of the ranges (we're not interested in the actual resistance here, just if there's continuity) or you'll want the tone test (which is when you stick the 2x probes together, the tester makes a noise).

This next bits crucial to do the test correctly: you'll need to disconnect one end of the fuse link. This ensures you don't have a false-positive result, such as a separate circuit giving you a false reading.

Put the 2x probes on either end of the fuse link ends. If you've got a reading of zero, anything such as 32.6ohms for example, or even a tone from the tester = this means the fuse is ok and has not broken (or fused).

If however the tester doesn't make a tone noise, or says something similar to >2000ohms for example. It means there is no continuity and that the fuse has broken and warrants a replacement.

Sorry it's long winded. Reply on here if you need further explanation or DM me 👍
I got around to testing them this morning, I'm not to sure what each one does due to the cover being pretty worn but from Top to bottom:
The first one has continuity
The second one only had one thing? Didn't really know what to attach the probes to or anything
The third one had continuity
The fourth one looked strange
Looking at a diagram online I think the fourth one is labeled BAT. I didn't try and pull it out or anything because it didn't have covers like the rest, it was just wire. But it was a lot stiffer than the wires going to the other ones.
 

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MCBladeRun

Club Member
I got around to testing them this morning, I'm not to sure what each one does due to the cover being pretty worn but from Top to bottom:
The first one has continuity
The second one only had one thing? Didn't really know what to attach the probes to or anything
The third one had continuity
The fourth one looked strange
Looking at a diagram online I think the fourth one is labeled BAT. I didn't try and pull it out or anything because it didn't have covers like the rest, it was just wire. But it was a lot stiffer than the wires going to the other ones.
Gosh, I'll admit now that I'm not 100% sure what your image is showing. I could hazard a guess but I don't want to lead you down the wrong path, so take it with a pinch of salt:

The BAT wire, which is bigger than the others, looks like it could well be a fuse wire - it seems to be connected in there via spade connectors by the looks of it. My view is that is a main fuse for that neat little box.

The plugged in bits must be a type of fuse? Possibly a fuse carrying connector. You might have to unplug them to find they're individually fused.

Unless of course that BAT wire you identified is the only fuse and those are just connectors? You'd have continuity regardless on the 1st and 3rd wires as, they probably supply the same circuits.

Sorry bud, will have to wait and see if anyone else on the forum has experience or can identify the parts in your photo.
 

jacoLiz

Forum User
Gosh, I'll admit now that I'm not 100% sure what your image is showing. I could hazard a guess but I don't want to lead you down the wrong path, so take it with a pinch of salt:

The BAT wire, which is bigger than the others, looks like it could well be a fuse wire - it seems to be connected in there via spade connectors by the looks of it. My view is that is a main fuse for that neat little box.

The plugged in bits must be a type of fuse? Possibly a fuse carrying connector. You might have to unplug them to find they're individually fused.

Unless of course that BAT wire you identified is the only fuse and those are just connectors? You'd have continuity regardless on the 1st and 3rd wires as, they probably supply the same circuits.

Sorry bud, will have to wait and see if anyone else on the forum has experience or can identify the parts in your photo.
Hmm.. Yeah I'm not 100% either. Looking at other z31's it looks like it has similar connections to spots 1 - 3 in that fourth spot. Maybe something happened there and the previous owner did some type of strange 'fix'?
I saw online there was a upgrade where you could replace the fusible links with regular old fuses but I think it might take a generous amount of electrical biz to get installed and working.
I think I might just order the fusible link that is supposed to be in that fourth slot, maybe try and make it work that way? My only qualm is that the battery appears to work just fine, I can start the car and drive it around blinkers, cruise control, and all. I am just missing a lot of vital info and some accessory stuffs. So if that is the case than replacing that 4th slot will probably just do nothing.
Thank you for all of the help though! And sorry for my rambling. I'll get back to lookin around!
 
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