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Fusible Links Smoking


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I'm back to work on my 78 280Z.  It's from an estate and many items were removed under the hood by previous owner who wanted th "clean up" some things.   I do have some history of the car having helped the owner in the past.  Although it ran and passed a leak down and compression test withflying colors it had a number of things that needed attention.  The major things i've done so far are installing new starter, alternator, distributor with fast xr3000 ignition module with distributor internals and matching Fast coil along with new plug wires, etc., new water pump and radiator, hoses, belts, removed all the old air cond. system parts under the hood, blocked off the ERG system, etc.  I just picked up where previous owner left off and really cleaned up along with some painting under the hood.  Upon attempting to start the engine for the first time the fusible links under the two white plastic covers on left side produced some smoke so I stopped trying.  I removed the four fusible links and they all tested good for continuity.  I suspect that I should replace them because even though they tested good, some of thier insulation looked somewhat melted.  But, I still need some ideas of what may have caused this.  Could I have wired the alternated wrong?  I can't imagine this problem being related to the new ignition system that I installed.  Where else should I look?  

Edited by mayolives
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  • mayolives changed the title to Fusible Links Smoking

1 hour ago, mayolives said:

Upon attempting to start the engine for the first time the fusible links under the two white plastic covers on left side produced some smoke so I stopped trying.  I removed the four fusible links and they all tested good for continuity. 

They worked!  Yay.  The melting (fusing) process can be incomplete.  Even a single strand of wire remaining will show continuity so that not a good sign of viability for future use.

Check the fusible link for the EFI system also.  It's connected to the positive post at the battery.  78 used two greens side-by-side, exposed.  Also make sure that you didn't get the EFI wires switched.  They used the same type of connectors for negative and positive.  (Genius!).  Hopefully you didn't fry the ECU.

All of the things you touched have the possibility of reversed positive and ground.  Even at the starter.  These old Z's are well known for using red and black indiscriminately on the big cables, for some odd reason.

1 hour ago, mayolives said:

The major things i've done so far are installing new starter, alternator,

 

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Quote.    "All 4 were smoking? They are on different systems so that is odd."

It looks like the black wire was the hot one due to the discoloration on the white plastic cover.

I ordered a set of new fusible links from Zcardepot. 

I used the original battery cable that were in good condition. 

I suspect that I may have wired the new alternator wrong.  Thanks for the advice. 

To be continued.  

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Hey, I had this exact same instance last month on my '72. (Did you get your alternator from ZCarDepot by chance?) due to my car having the + wire on a small eyelet, and the ground wire on the large eyelet, I wired the alternator the opposite of what it should have been. I only had the battery connected for maybe 5-10 seconds, but it was enough to smoke the sheathing off the fusible link. I've replaced the fusible link, but I now read, from battery + harness to alternator + 0ohms, and from battery + harness to alternator ground, 3 ohms. I have a hunch that I also burned off some insulation in the wiring loom, and have a short. so be careful there.... I am planning on ripping open the wiring loom, and re-running ground and + wires to alternator, just to be safe. 

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I believe my new alternator may have been one of the new parts I received with the car because I don't have a purchase reciept in my file.  I did compare it with the old one and all terminals were in the same location, etc.  Hopefully my new links will arrive so that I can carefully go about tracing some wires before giving it another try. 

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Photos of the connections you have at the alternator would be nice. @Wally posted photos, and it didn't take more than a second to see where he went wrong.

While you're at it, post photos of the battery with cables.

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14 hours ago, mayolives said:

Hopefully my new links will arrive so that I can carefully go about tracing some wires before giving it another try. 

For this kind of problem i have automatic fuses.. that way you will not burn your new links!  Instead of 1 try you can simply reset the fuse

So install a temporary fuse, could also be a fuseholder with a suitable fuse of the rating of your link! 🙂

btw if you burn links your car has a big problem, normally only a fuse blows when there is a problem in the electric department..

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On 10/14/2021 at 2:43 PM, Zed Head said:

 

Zed Head...... I took your advice and ordered a few circuit breakers.  Handy dandy items!  I'm going to take a cloce look at my alternator wiring this afternoon.  Hope it has been wired wrong. 

 

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After looking at my Body Electrical System diagrams in my FSM for ever and a day, I haven't found what fusible link protects what circuit.  These are the ones on the left front fender under the hood and have white plastic covers.  Look like the black one position outside/front was in the worst condition.  I sure would like to find this in my FSM or have some advice.   

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36 minutes ago, Zed Head said:

Can't remember your year of car or I'd post a link but the big full-car wiring diagrams show the fusible link circuits.

 

He did say in the first post that it's a 78. I've missed the year being posted in other threads, too. We're just getting old, @Zed Head. LOL 

That aside, @mayolives, here is one way to test:

  1. Disconnect your battery at the positive and negative terminals.
  2. Disconnect the alternator wires. Make sure you pay attention about which wire went where.
  3. Remove all 4 fusible links. Make sure you pay attention about which link went where.
  4. Use an ohmmeter to measure resistance from the connector at the fusible link block to ground. Put the probe on the connector that goes to the white/red wire on the underside of the block. Record your readings. Do that for all 4 positions.
  5. Report your readings. Use the post by @Captain Obvious to indicate which reading was at which fusible link position.

Repeat the above steps but with the alternator connected.

If you see a low resistance reading, that would indicate a short. Here is what it looked like when I was measuring at the connector for the fusible link in my 73 to ground. (878 Ohms)

20211018_165730.jpg

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16 hours ago, mayolives said:

Hope it has been wired wrong. 

I'm almost sure thats the problem ..

Btw.. the circuitbreaker was eh... my idea.. and i'll give you another one..  I made one parallel over a old blown fuse (those big glass fuses that are used in a 240z) and then you can click it right into the fusebox on the circuit you want to test.. ( I soldered the circuitbreaker to it.. went very well)

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