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dmoralesbello

280Z Restomod Progress

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I had an electrical mishap after "finishing" my engine bay. I inadvertently pinched a cable (in front and below the windshield cowl) while tightening one of the brackets that I powder coated on the firewall. I caused a short circuit which toasted a dozen or so wires in the harness. It took me a couple of months to figure out the cause of the damage and then replace all the scorched cables with ones form a donor harness I was lucky enough to find on Ebay. Definitely not a fun job.

The thing is that although the fusible links heated up and melted the insulation during the short circuit, they never broke! Electricity continued to flow and burn stuff until I was able to yank the positive terminal from the battery. It was about 30 seconds of pure panic and smoke. Thankfully no fire!

After repairing the wire loom and testing everything I decided to get rid of the fusible links and replace them with a modern fuse block and Maxi fuses (as discussed in other posts). Hopefully this setup will grant me better protection in the future. Here's a pic.

PS: The fuse holder above the fuse block is for my stereo equipment.

 

 

Fuse block replacement for fusible links.jpg

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38 minutes ago, dmoralesbello said:

The thing is that although the fusible links heated up and melted the insulation during the short circuit, they never broke! Electricity continued to flow and burn stuff until I was able to yank the positive terminal from the battery.

 

Sounds like they weren't really fusible links.  Do you know that they were the factory originals or were they aftermarket?

 

Could also be that somebody used the wrong links.  There's been a discussion over the years about the use of the red links in place of the brown ones.  Many years ago somebody decided that the brown ones were actually red and that they were 50 amp capacity instead of, probably, 30 amp.  This red link information has been propagated since then even though the FSM clearly shows different, with a smaller gauge wire for the Brown (Br) links.  Maybe somebody finally got "burned" by it.

 

Bummer.

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Forgot to say that if you had the incorrect fusible link because of that bad information and replaced the link with a fuse of the same amp rating, then you'll be in the same situation.  You haven't really improved anything.

 

I see three 50A fuses in your picture.  Those are way too high.  Compare the fusible link wire sizes in the FSM and you'll see that the Brown links can't be 50 amp, if the Green links are 40 amp.  Brown is smaller than Green.

 

Here's the info from the 1978 FSM that I'm talking about and the other info about "red" links.  That were never used.  I don't know how it got this way but Nissan's FSM's were the same for many years, showing Brown as the smallest link, and never showing a Red one.  This topic was one of my first big discussions on a Z forum.  Never did get a good answer.  The atlanticz page even shows wire size, that doesn't match the FSM's.

 

http://www.atlanticz.ca/zclub/techtips/fusiblelinks/index.html

 

image.png.c908127a11d41c390fa4f20268caa726.png

 

image.png.e8360afee35152b9c2aaab01efe030df.png

Edited by NewZed

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14 hours ago, NewZed said:

Forgot to say that if you had the incorrect fusible link because of that bad information and replaced the link with a fuse of the same amp rating, then you'll be in the same situation.  You haven't really improved anything.

 

I see three 50A fuses in your picture.  Those are way too high.  Compare the fusible link wire sizes in the FSM and you'll see that the Brown links can't be 50 amp, if the Green links are 40 amp.  Brown is smaller than Green.

 

Here's the info from the 1978 FSM that I'm talking about and the other info about "red" links.  That were never used.  I don't know how it got this way but Nissan's FSM's were the same for many years, showing Brown as the smallest link, and never showing a Red one.  This topic was one of my first big discussions on a Z forum.  Never did get a good answer.  The atlanticz page even shows wire size, that doesn't match the FSM's.

 

http://www.atlanticz.ca/zclub/techtips/fusiblelinks/index.html

 

image.png.c908127a11d41c390fa4f20268caa726.png

 

image.png.e8360afee35152b9c2aaab01efe030df.png

I think you hit the nail on the head. The fusible links I had before were put there by the previous owner and I assumed them to be correct. I seem to be making a similar mistake now with the Maxifuses as you point out. Should I be using 30 amp fuses to replace the three 50 amp ones and a 50amp instead of the 80 amp fuse? 

In

I'm very thankful for your input and correcting my error. 

Dave

Edited by dmoralesbello

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It's hard to say.  Because it's not clear that the conversion from wire size to amps is correct.  If you assume that the conversion is right, then actually a 20 amp might be right. 

 

0.3 mm is 43% of .69.  43% of 50 amps is 22 amps.  Or, 60% of the green link, 0.3/0.5, gives 24 amps.  So, 20 or 25 seems right.

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