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Fusible Links Smoking


mayolives

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15 hours ago, Zed Head said:

If your car was or is an automatic there are two inhibitor devices that could be shorting

This is an originia five speed car sold new in CA.  Sounds like I need to start with the ignition switch and then the ignition relay and go from there.  

Edited by mayolives
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On 11/18/2021 at 7:18 PM, SteveJ said:

Cut down some of the wiring you're trying to trace.

Pull the ignition relay. It's around the passenger kick panel

 

On 11/18/2021 at 7:18 PM, SteveJ said:

Put in another 30A fuse. Turn the key to ON. See if you smoke the fuse again. If not, get with me on tracing down the short downstream of the relay.

I disconnected the ignition relay and the new 30amp fuse blew out when I moved the ignition key to the on position.  Although I didn't check the wiring from the ignition switch as New Zed suggested, I did install a complete new switch and cleaned up the combination switch connections.  I want to work on one possible area at a time in order to not confuse the situation.  I'm not sure where to go from here.  Even after decades of playing with z cars, my understanding of electrical testing is not good.  I've installed painless harnesses by following instructions and can usually wire most things from one point to another buy I'm dumb as a rock about relays, etc.  I do have a good digital multimeter and a power probe III.  I'll need some "spoon feeding" in order to trace this problem.  

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Here is what I suggest doing:

  1. Keep the Ignition Relay unplugged.
  2. Make sure the headlights, wipers, etc. are off. Close the doors
  3. Remove the fuse.
  4. Put your multimeter on resistance.
  5. Put the key in Accessory.
  6. Measure resistance to ground from the side of the fuse opposite from the battery. (Wiring harness side)
  7. If resistance is less than 1 ohm, that would indicate a short in the wiring harness.
  8. If the resistance is greater than 1 ohm, turn the key to ON.
  9. Measure resistance to ground from the side of the fuse opposite from the battery.
  10. If the resistance is less than 1 ohm, unplug connectors C-3 and C-2.
  11. Measure resistance to ground from the side of the fuse opposite from the battery.
  12. If resistance is less than 1 ohm, that would indicate a short in the wiring harness.
  13. If resistance is greater than 1 ohm, disconnect the black/white wire from the coil positive.
  14. Reconnect connectors C-3 and C-2.
  15. If resistance is greater than 1 ohm, I would hazard that something is wrong with the aftermarket ignition. (wiring, bad component, etc.)

 

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This might help.  I only see four other things that could be connected directly to ground, or have an internal short.  The diagram does have an odd parallel circuit in it, for anyone that likes a puzzle.

Many ways to figure out a problem.

 

 

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In the spirit of "it's probably related to the last thing you messed with"... Didn't you recently mess with the B/W wires over at the ballast resistor and at the stock ignition box? If so, I suspect you've got a short to ground on one of the B/W wires.

Why do I say that? Because a) You messed with them right before this latest problem started, and b) those B/W wires go hot when the ignition key goes to the ON position. If one of them is connected to ground somehow, you'll pop the front inboard fusible link.

Just a thought without a lot of research.   

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10 hours ago, Captain Obvious said:

In the spirit of "it's probably related to the last thing you messed with"... Didn't you recently mess with the B/W wires over at the ballast resistor and at the stock ignition box? If so, I suspect you've got a short to ground on one of the B/W wires.

Why do I say that? Because a) You messed with them right before this latest problem started, and b) those B/W wires go hot when the ignition key goes to the ON position. If one of them is connected to ground somehow, you'll pop the front inboard fusible link.

Just a thought without a lot of research.   

That's kind of what I was thinking with the Crane ignition being factored in, but you probably saw where I was heading with my diagnostics. 

It is personal operating philosophy to first eliminate the last thing I f'd with.

  • Agree 1
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14 hours ago, SteveJ said:

Measure resistance to ground from the side of the fuse opposite from the battery. (Wiring harness side)

Is this measurment taken from the actual fuse holder where I removed the blown fuse?

 

15 hours ago, SteveJ said:

Measure resistance to ground from the side of the fuse opposite from the battery.  

Do you mean the side of the fuse closest to the front of the car?

 

15 hours ago, SteveJ said:

If the resistance is less than 1 ohm, unplug connectors C-3 and C-2

Wher are connectors c-3 and c-2  

 

1 hour ago, SteveJ said:

It is personal operating philosophy to first eliminate the last thing I f'd with.

I suspect that you guys are correct on this one.  A few more test hopefully will tell the story!

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One side of the fusible link connects to the battery. (I said fuse because you wanted to connect the fuses in place of the links.) The other side connects to the rest of the wiring harness. Look under the fusible link block. One side has a white wire (battery), and the other side has a white/red wire (wiring harness). Go on the white/red side of the fusible link block for your measurements as you want to be able to see when the harness is shorted (to ground).

This is the stock location of C-2 and C-3.

image.png

C-2 is black. C-3 is green.

FYI: all of this information comes from the BE section of the FSM and the wiring diagram. The FSM can be downloaded from this site. Please see the link in my signature or go to the Resources section of the website. @Zed Head posted the wiring diagram in this thread.

If you follow my instructions carefully and exactly, there is a good chance you will narrow down where the short is located. If you are having problems, I sent you a PM on how you can contact me.

 

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16 minutes ago, SteveJ said:

This is the stock location of C-2 and C-3.

So looks like these connections are located under the right footwell.  I do have the 78 FSM but at times, especially when dealing with wiring items, it reads to my dumb arse like hieroglyphics.  Thank you for your help.

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  • 2 weeks later...

I have gone through several test that were spoon feed to me in order to locate my short that continued to blow the fusable link related to the ignition system. Sure enough these resistance test led me back to where the trouble started.  That was the area of the new fast ignition system that I had installed.  I discovered a black ground wire that was attached to the base of the distributor was attached to a hot wire that was activated when the ignition was switched to the on position.  It had a bullet connector that I had mated to black w/ blue stripe wire.  Also, I discovered my new coil was not connected to any power source from the cars electrical system.  After looking at the diagrams in the EE section of my FSM, I still can't determine where several wires in this area belong.  I have colored wires that don't match the ones in the FSM and still need some advice.  

In the photo below there are five wires.  Moving from left to right (front to back) I have listed the colors.

black w/ white stripe ( has blue shrink wrap on end)... It is hot when key is in on position.

green (has blue shrink wrap on end) 

black w/ blue stripe  It is hot when key is in on position.

blue

white

I have reconnected everything in the footwell of the cabin except the ignition module.  Two of these wires must have gone to that module, and I will need a power source to the coil.  Some advice would be greatly appreciated.     

 

280z five wire 2.jpg

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