260z fusible link to maxifuse upgrade question

[Hypertek]

So my fusible link box was in pretty bad shape. I went out and purchased a 2 fuse maxifuse block from walmart, which I want to install.

Now the thing is the 74 260z is a little different from all the write ups Ive seen done on the maxifuse upgrade on 240s and 280s. I seen maybe 1 or 2 people mention they done it from doing a google search, but no specifics on how it was done.

I stripped the wiring harness back. I removed the white wire that went from the starter positive to the fusible link. I am going to run an 8 gauge power wire from the battery direct to my new maxifuse block. The other end of the white wire (that was originally fused to the fusible link) i will hook that up to the new maxifuse block. But what I am stuck on is the white/red wiring. 2 of those wires seem to run into the interior side of the harness from what it looks like, while 1 of them is spliced towards the alternator (im assuming)

I know someone out there has to have done the 260z upgrade. Hopefully you guys can help me with it. People been telling me to look at the fsm, but i don't understand it.

[Mike W]

I have done this on a 260Z, but also bear in mind that mine is a very late version (typically known as 74 1/2) and so there may be some differences.

Having said that, the wiring diagram I used from the FSM was from a 74 so there should be good correlation. I have attached a PDF showing a simplified version of how it was wired from the factory as well as how I rewired it with a new external fuse block. I've also included a picture of the fuse block install as well.

Hope this helps.

Fusible Link Replacement OEM Wiring.pdf

Fusible Link Replacement New Wiring.pdf

[Hypertek]

Thanks for the quick reply. Your setup looks great. I suppose though that you did all the homework and rewired the whole thing huh?

I kinda get the idea though, to wire the fuse box somewhere before the original location. I am still a bit lost though

[Hypertek]

ok I think I see it now, I can do it this way. let me know what you think. Should be simple enough.

I did a quick edit to your picture if you don't mind.

[FastWoman]

Hyper, I'm unfamiliar with the 240 wiring, but I did my '78 280 rather simply, somewhat like you show. I attached a second battery cable from the starter post to the maxifuse block. I then had one fuse for each circuit (mostly white and white/red wires -- the later 280 having about 6 circuits, as I recall). Then I added a back-feed circuit just for the alternator, with a generous ampacity of fuse -- 80A as I recall. I connected this circuit directly to the alternator with a new, heavier gauge wire (6 awg, as I recall), stripping out all the awful (factory original) mess of branched white/red wires. I think I used my 8th fuse position for my stereo system.

Mike, I think that looks like a modern, digital flux capacitor! I assume the digital display gives you both voltage and amperage readings Very slick.

Edited January 24, 2014 by FastWoman

[Mike W]

Hypertek,

I do not think that edit is correct as the original fusible links were powered separately and each link protected a certain part of the electrical wiring system. At least that is how my car was originally wired and I spent an inordinate amount of time trying to get these diagrams correct. However, with the replacement fuse block that I used, the input feeds are ganged together and so there is only a single supply source that I use with the new fuse block. That is why you see them connected together in the "new" wiring diagram. Let me know if you have any other questions on this and I'd be happy to help you out. From my experience, this looked like it was going to be a lot more complex than it actually turned out to be. A couple of other points as well.

1. Your car still has the "shunt" which is used to drive the ammeter in the car. You will need to hook this up correctly so you still get accurate readings for charge / discharge on your ammeter.

2. Not shown in my diagrams is an alternator upgrade that I also completed as a part of this. It simplified the wiring significantly as I used a "one wire" alternator that is internally regulated so I was able to remove the old mechanical voltage regulator as well as associated wiring, and the new alternator wiring was simply a single wire from the charge output to the battery. Couldn't have been easier and the improvement in the performance of the electrical system is like night and day. Went from a 60 amp output to 140 amp so I have plenty of available charging power if I need it. Happy to give you the details of this if / when you need it.

Sarah,

Yes the fuse block I chose is very cool and adds a nice look to the engine bay. On top of that, you are 100% correct that it will also display both voltage as well as current (alternates between the two) and this can be very handy at times when trying to troubleshoot an electrical issue. I am happy to get you the details of this block (manufacturer, etc) if you are interested. I spent a lot of time looking for something like this but this is the product I ended up with. Very happy with it so far and certainly a vast improvement over the worn out fusible link system that was in my car.

Hope that helps.

Mike.

[FastWoman]

Thanks, Mike, but mine is already done. It looks cool, too, but not THAT cool!

I think wiring the ammeter shunt in series with the cable I describe between the starter and the maxifuse block would achieve the same thing. It would account for the total current budget to and from the battery, minus what is dumped into the starter. It would be roughly equivalent in function to what you have diagrammed. As Hyper has re-diagrammed, the ammeter would not read current to the ignition circuit.

If the ammeter in the 240 is wired like most ammeters, I suppose your main supply wire goes into the dash, connects to one post of the ammeter, conducts to the other post via the shunt (which is bolted between the two posts), and then makes a return loop back to the fusible link block. Is that correct? (I wouldn't know, because the '78 280Z has a voltmeter, not an ammeter.)

If this is your situation, you can rewire your ammeter as follows, thereby reducing voltage drop and lightening up on wire requirements: First, remove the shunt from the back of the ammeter, and transplant it to run in series with the cable between the starter and the maxifuse block. Remember that it will get warm/hot, so be mindful of the materials you use to make the mount for the shunt. After you've done that, run a couple of small gauge wires from the two sides of the shunt to the two sides of the ammeter (which becomes a simple galvanometer without the shunt attached). This eliminates the current loop to the dashboard and back (and the corresponding voltage drop).

My '66 mustang had a very clever way of measuring current. It used the main supply wiring as the shunt, and it ran wires from the two ends of the supply wire (e.g. on the starter and on the fuse block) to the galvanometer ("ammeter"). This is a fussy sort of configuration and requires the right gauge of supply wire to create the right voltage drop for correct ammeter readings. But by eliminating the shunt, they eliminated just a bit of voltage drop. They eliminated even more voltage drop by shortening the main current path. And it worked fine. Very clever!

[FastWoman]

FAIW, here's an external ammeter shunt, pre-made:

Stewart Warner Ammeter Shunt 413717 | eBay

If you substitute the shunt strip from the ammeter in your dash, the gauge readings should be correct. And of course you could make something like this pretty easily. Search Ebay for "external ammeter shunt" for other possibilities, including some $5 made-in-China units.

[FastWoman]

Here's the thread on mine, BTW:

http://www.classiczcars.com/forums/electrical-s30/35588-upgrade-fusible-links-circuit-breakers.html

(The title of the thread is misleading, since I went to fuses instead of breakers.) Scroll way down for pictures. I also did a headlight relay upgrade, diagrammed in that thread.

[rcb280z]

Hey Mike, I am interested in the fuse block. Where did you get it?

Bob

[Hypertek]

if i swap to a 280z voltmeter , than i should be good right? Most of my cars have ran with voltmeters, so i prefer that setup . I also plan to swap to a 90amp maxima alternator (i should have picked one up when i was at the junk yard).

[Mike W]

Bob,

The part is made by DB Link / Strandflex and the part number is SFANLFB12DA. It uses mini ANL fuses and is very well made. I am happy with the product as well as the upgrade. You can get it am Amazon here:

Amazon.com: DB Link SFANLFB12DA Strandflex 2-Position Digital Mini ANL Fuse Holder: Car Electronics

Not bad for $32.

A few other comments on the ammeter / shunt as well.

I believe that Nissan changed the size and location of the shunt over time. I recall that in the early Z cars the shunt was actually located behind the gauge itself, while in later years (not sure exactly when this started), the shunt was moved to the engine bay and the physical size of it grew significantly. I suspect that this had to do with the ever increasing electrical capacity in the car and the need for a much heftier shunt resistor to measure current for the meter. I also suspect that this is why they ultimately moved to a volt meter (like in Sarah's car and the later 280's).

In any case you can see most of the shunt in the picture I included above with the new fuse block. It is the large silver box just below the fuse block and it houses a very large resistor / shunt that is capable of passing all of the current that the car requires.

Mike.