Fusible Links Smoking

[mayolives]

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.   

[Captain Obvious]

Not a very detailed list of which fusible link does what, but this should at least get you started:

 

 

[Zed Head]

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.

[SteveJ]

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.  

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)

[dutchzcarguy]

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)

[mayolives]

I check my alternator and starter connections and they are good.  Also I purchased curcuit breakers to continue my test with.  They have small male ends that would need to be adapted to the wide male ends where the fusible links plug into the car.  Too much of a pain in the a## to deal with cobbing together by soldering, etc.  The easiest way for me to protect the circuits and not waste my oem fusible links is to just link the curcuits together with blade type fuse holders for each of the four curcuits.  I'm not sure what amp fuses to use because I can't find the amp ratings for the oem fusible links in my FSM.  Where are they listed?     

[mayolives]

Perhaps my question just above was not very clear.  Fusible links are shown in many, many diagrams in my FSM.  Also the fuse block shows up in many diagrams.  The FSM shows the fuse amp rating/sizes for the block but does not show the fusible link amp ratings.  I'm using blade type fuse holders to plug into the fusible link connections under the hood in order to do some test without blowing my new replacement oem fusible links.  I don't know what size fuses to use for my test.  Any idea of the fusible link ratings?   

[mayolives]

I researched the topic at Hybrid Z (2018) and found a discussion that New Zed and others commented on. This is what I found:

     Based on wire size alone                          Based On member "dmoralesbello" trials

    AWG 12  fuse up to 20A                        60 amp in the largest wires position

    AWG 10  fuse up to 30A                        30 amp in the other 3 positions (wanted to use 25 amp but could not find)

    AWG 8   fuse up to 50A

    Others felt that 25 amp fuses should be used

I 'm still undecided about fuse sizes but seams like 25 amp is a good place to start but I'm really open suggestions and thoughts from those who know more about this subject.  

[SteveJ]

What are you testing for? Are you looking for short circuits, or are you trying to find out how big of a fuse you can put in the circuit before it blows?

Have you tried what I suggest in post #16?

[mayolives]

Quote: What are you testing for? Are you looking for short circuits, or are you trying to find out how big of a fuse you can put in the circuit before it blows?

All the above.  I'm going to test with my ohmmeter for shorts and also try to determime what size fuses will work.  Eventuall, I will install a fuse block to replace the original fusible link set-up.  I do know some about it's history and it did run good not long ago.  This car was non-running when I purchased it and had so many items removed from under the hood. I'm taking it one step at a time to not create more questions until I get it running.  It has great compression, fresh valve job, new injectors and ignition system so it should run really good. I'm stall puzzled about why the links failed when I first tried to start the engine but hopefully I'll find the reason soon.  

[mayolives]

Steve J...QUOTE:

  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.

_____________________________________________________________________________________________

I completed the above test with my ohmmeter buy I'm not sure what the test has revealed.  With the alternator disconnected the only reading I had was at the outside front fusible link connection that is for the alternator.  It read 1.84.  The other three connections had no readings.  With the alternator connected the alternator connection read 1.032.  The other three again had no readings.  What does this test tell me?  Is this new alternator bad?

Also, I checked all the fuses in the fuse block at the passenger foot well.  They were all in good shape. 

Although I have made up inline fuse holders to temporarily replace the fusible links, I have not tried to start the car until I determine what caused the links to "smoke" when I last tried. 

[Zed Head]

On 10/9/2021 at 11:03 AM, mayolives said:

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.  

IF you highlight the text you want to quote a green box should show up.  Click the box and you'll get a reply box with the text inside.

 

Could you describe what is working now and what is not?  Lights, ignition, etc.  Do you have any of the breakers installed?  Also describe or show your battery connections, including the links for the EFI system.  The two green fusible links at the battery positive post.

Might as well start at the beginning, the battery, and see what you have.  Seems like things are pretty messed up.