[JBensyl]

Ok I have a new M&H engine harness to install, but I have a question.

There is a black wire labeled fuse link 16g folded up and half way wrapped back into the harness by the alternator wires.

Where does this wire connect to? I ask because I don't have this on the old harness that has been butchered. I do have a wiring diagram but I don't see that wire on there.

Thanks for any help.

[FHummel]

Originally Posted by JBensyl

Ok I have a new M&H engine harness to install, but I have a question.

There is a black wire labeled fuse link 16g folded up and half way wrapped back into the harness by the alternator wires.

Where does this wire connect to? I ask because I don't have this on the old harness that has been butchered. I do have a wiring diagram but I don't see that wire on there.

Thanks for any help.

To begin with I suggest that you contact M&H as to their intended use of that wire.

That said, a fuse link (which in an OEM harness is a calibrated length of a certain gauge wire, so don't cut it shorter if it is to be used) is used for the standard distributor/coil setup, in which case there are effectively two wires feeding the coil + from the ignition switch: one is the fuse link (in your case a piece of 16 gauge wire) that limits the voltage to the coil to approximately 7-8 volts in the RUN position (when the points are closed) of the switch (#1 position); the other wire (probably 14 gauge) feeds from #2 position (START) to supply a full 12 volts for starting only. (Remember that the lower the number of the wire gauge, the larger the wire - a larger wire carries more current than a smaller wire with proportionately less voltage drop.) Aftermarket ignition systems (i.e., MSD, etc.) and HEIs use the full 12 volts for RUN and START. I'm not sure on the '67 GTO if you actually have two wires going to the + on the coil in the OEM wiring, or if it is actually buried in the harness such as the '65 GTO, in which case the resistance wire coming from the RUN/IGN#1 position is spliced to the START wire (back in the harness and is not visible unless you unwrap the harness) and another length of wire is also spliced-in to continue on to the + side of the coil thus apparently having only one wire to the coil rather than two.
I hope this was not confusing.
Again, contact M&H and ask them about that resistance wire in their harness.

Frank

[screamingchief]

Originally Posted by FHummel

To begin with I suggest that you contact M&H as to their intended use of that wire.

That said, a fuse link (which in an OEM harness is a calibrated length of a certain gauge wire, so don't cut it shorter if it is to be used) is used for the standard distributor/coil setup, in which case there are effectively two wires feeding the coil + from the ignition switch: one is the fuse link (in your case a piece of 16 gauge wire) that limits the voltage to the coil to approximately 7-8 volts in the RUN position (when the points are closed) of the switch (#1 position); the other wire (probably 14 gauge) feeds from #2 position (START) to supply a full 12 volts for starting only. (Remember that the lower the number of the wire gauge, the larger the wire - a larger wire carries more current than a smaller wire with proportionately less voltage drop.) Aftermarket ignition systems (i.e., MSD, etc.) and HEIs use the full 12 volts for RUN and START. I'm not sure on the '67 GTO if you actually have two wires going to the + on the coil in the OEM wiring, or if it is actually buried in the harness such as the '65 GTO, in which case the resistance wire coming from the RUN/IGN#1 position is spliced to the START wire (back in the harness and is not visible unless you unwrap the harness) and another length of wire is also spliced-in to continue on to the + side of the coil thus apparently having only one wire to the coil rather than two.
I hope this was not confusing.
Again, contact M&H and ask them about that resistance wire in their harness.

Frank

Uhh,sorry to point this out,but it seems that you're the one that's confused?

The purpose of the fusible link and the resistance wires are not one & the same,they are two completely seperate items that really have nothing to do with each another.

Fusible links are circuit protection,nothing more and nothing less.

They protect a given circuit(s) from shorts and nothing more.

The resistance wire just limits the "run" voltage to the coil.

And all the resistance wire does is drop the voltage in a given circuit.

The two are completely seperate items.

The resistance wire to the coil is typically run to the fuse block itself,and that voltage to the fuse block is supplied by the ignition switch,not by the fusible link.

Typically the second coil + wire that runs to the start terminal on the solenoid is spliced directly into that resistance circuit for the coil right @ the coil + terminal,as a means to bypass the resistance wire's circuit and boost the start voltage to 12+v for faster starting.

The fusible link is typically way over on the other side of the fuse block,and it's over there to protect the harness itself should there be a short to ground anywhere in that harness,that link is one of the main power feeds to the rest of the electrical system,so it typically feeds pretty much everything,the fuse block,the ignition switch,you name it,just remember that the fusible link is on the complete opposite side of the system than the resistance wire is,so in no way can it really be said that the fusible link limits the current going to coil,when that is infact being done by the resistance wire instead.

Typically the fusible link is tied into the wiring that runs directly to the battery current,though it can do this at any one of several points,often @ the starter solenoid or at other times at the main harness splice,it kinda depends on the given system one is dealing with and how it was wired up originally.

A fusible link would come before the fuse block or the ignition switch or such.

The coil's resistance wire would come after the fuse block or the ignition switch.

Either way,I agree if one is not sure where the fusible link should go,call M&H and confirm where it belongs,as a mistake there could render the entire harness @ risk,and could potentially lead to an electrical fire if there were an unexpected short somewhere.

FWIW

Bret P.

[FHummel]

Originally Posted by screamingchief

Uhh,sorry to point this out,but it seems that you're the one that's confused?

The purpose of the fusible link and the resistance wires are not one & the same,they are two completely seperate items that really have nothing to do with each another.

Fusible links are circuit protection,nothing more and nothing less.

They protect a given circuit(s) from shorts and nothing more.

The resistance wire just limits the "run" voltage to the coil.

And all the resistance wire does is drop the voltage in a given circuit.

The two are completely seperate items.

The resistance wire to the coil is typically run to the fuse block itself,and that voltage to the fuse block is supplied by the ignition switch,not by the fusible link.

Typically the second coil + wire that runs to the start terminal on the solenoid is spliced directly into that resistance circuit for the coil right @ the coil + terminal,as a means to bypass the resistance wire's circuit and boost the start voltage to 12+v for faster starting.

The fusible link is typically way over on the other side of the fuse block,and it's over there to protect the harness itself should there be a short to ground anywhere in that harness,that link is one of the main power feeds to the rest of the electrical system,so it typically feeds pretty much everything,the fuse block,the ignition switch,you name it,just remember that the fusible link is on the complete opposite side of the system than the resistance wire is,so in no way can it really be said that the fusible link limits the current going to coil,when that is infact being done by the resistance wire instead.

Typically the fusible link is tied into the wiring that runs directly to the battery current,though it can do this at any one of several points,often @ the starter solenoid or at other times at the main harness splice,it kinda depends on the given system one is dealing with and how it was wired up originally.

A fusible link would come before the fuse block or the ignition switch or such.

The coil's resistance wire would come after the fuse block or the ignition switch.

Either way,I agree if one is not sure where the fusible link should go,call M&H and confirm where it belongs,as a mistake there could render the entire harness @ risk,and could potentially lead to an electrical fire if there were an unexpected short somewhere.

FWIW

Bret P.

Hey Bret, you're right. Thanks for the correction. I did get my 'wires crossed' with that one.
Frank

[First Bird]

A 16ga fusible link is meant to melt when a 12ga wire gets too much current. 12ga wire was the size of main power supply wire in many of our old cars. I'm not sure how a 1967GTO's charge circuit is designed. On some cars there is a fusible link right off the alternator charge stud in case the voltage regulator fails - protects everything downstream from the alternator, which makes Direct Current, in case it makes too much current. That's how this amateur electrician understands it. I'll be watching to see what the smart people say about this.

[JBensyl]

Ok M&H told me the fuse link wire is internally connected inside the harness. So there is no other connection required. The wire is looped outside of the harness wrapping due to the required length specified by GM.

Thanks for replies and I hope this will help anyone else swapping harnesses.