Fusible link at the starter for the 12 AWG Purple wire?

[71CHEVYSHORTBED402]

Thought I read someplace it's advisable to add a fusible link at the starter for the 12 AWG Purple wire. Is this true?

I've also read fusible links are a smaller gauge wire (i.e., larger number (yikes)). For instance, a 12 gauge wire would use a 14 gauge fusible link, maybe even 16.......................However, the consensus of old gents @ NAPA says the fusible link gauge is the same as the wire you're working with (i.e., 12 uses a 12 FS). So yeah, I'm confused.

And for my most lame question, what's stopping someone from cutting this fusible link to size? Here's an image of the link. Thank you.

[VetteVet]

The purple wire going to the starter solenoid is directly linked to the fusible link on the passenger fender which connects to the battery positive. That is if some one hasn't replaced it with a solid wire. Once you turn the key to start the battery goes through the FL to the key switch to the purple wire.

The standard for fusible links is that the link must be 4 sizes smaller than the wire it is fusing. IOW a 12 gauge wire requires a 16 gauge link, an 8 gauge wire requires a 12 gauge link etc.

Ask the old farts at NAPA (I can say that cause I am one) which would burn out faster, a 12 gauge wire or a 12 gauge higher resistance, slow blow, fusible link.

You can cut the fusible link wire to any length but I believe there is a standard for the max length for a given size wire. I'll look and see if I can find it.

C/P from Google
Are there any general guidelines for choosing a suitable fusible link?
Typically, a given harness segment is protected by fusible link that is four gauge numbers smaller. A 14-gauge wire would be protected by an 18-gauge fusible link. A 6-gauge wire would be protected by a 10-gauge link, and so on. Odd number wire gauge sizes like 19, 15, 13 and 11 are counted when sizing a link. The length of a fusible link should not exceed 9".

[71CHEVYSHORTBED402]

Originally Posted by VetteVet

The purple wire going to the starter solenoid is directly linked to the fusible link on the passenger fender which connects to the battery positive. That is if some one hasn't replaced it with a solid wire. Once you turn the key to start the battery goes through the FL to the key switch to the purple wire.

The standard for fusible links is that the link must be 4 sizes smaller than the wire it is fusing. IOW a 12 gauge wire requires a 16 gauge link, an 8 gauge wire requires a 12 gauge link etc.

Ask the old farts at NAPA (I can say that cause I am one) which would burn out faster, a 12 gauge wire or a 12 gauge higher resistance, slow blow, fusible link.

You can cut the fusible link wire to any length but I believe there is a standard for the max length for a given size wire. I'll look and see if I can find it.

C/P from Google
Are there any general guidelines for choosing a suitable fusible link?
Typically, a given harness segment is protected by fusible link that is four gauge numbers smaller. A 14-gauge wire would be protected by an 18-gauge fusible link. A 6-gauge wire would be protected by a 10-gauge link, and so on. Odd number wire gauge sizes like 19, 15, 13 and 11 are counted when sizing a link. The length of a fusible link should not exceed 9".

Both my trucks have a regular 12 gauge wire that runs from the positive terminal to the junction block. The fusible link is on the block as well, as described below. Is this the fusible link you're referring to? I believe this is factory config., maybe not.

• 12 AWG red & fusible links configuration: A red wire runs from the firewall block to a splice. This wire is soldered with three additional 12 AWG red wires. One wire routes to the alternator, one wire to the voltage regulator, and one wire to a fusible link that attaches to the junction block. NOTE: The red wire from the firewall block also uses a fusible link near the splice.

Should you straighten the guys out or should I? Them boys been around forever. The oldest was near asleep anyway. Bit overwhelmed by the heat. So was I. It was not a productive day.

[VetteVet]

Your configuration is pretty much the same as the factory stock circuit.
They didn't use two wires from the battery positive to the fender junction and the fusible link was part of that wire.
There is nothing wrong with that system as long as no large current loads are added. The problem is that not too many of us are satisfied with the status quo.
We want electric cooling fans and high amp stereos or airbags with electric compressors. A 32 amp alternator or even a 61 amp just isn't going to cut it.
Neither will a 12 gauge wire being the largest size in the truck.

Here is the stock wiring just as it came from the factory. If you compare it with yours you can see that they are almost identical. If you have two small black wires, one at the fender junction and one at the alternator, battery, and regulator junction, they are for the battery gauge (ammeter) in the dash and you will have a gauge dash. if you have the light dash (idiot light) you won't have these two wires. The wire from the positive is mis labeled, it should be 12R if the link is longer than 9 inches. What they show is just the link and it should say 16B, four sizes smaller than the 12 gauge wire it protects.



This is just the charging system and doesn't include all the wires.

I have found that trying to argue with most people is an exercise in futility so I just listen to what they say and nod my head. You might get some place if you ask them why it says to use a FL 4 sizes smaller than the wire it protects.

[71CHEVYSHORTBED402]

I may have misunderstood what was written about the link. As for the NAPA folks, I simply asked what size was used. Then I piped up, but they disagreed. Incidentally, the existing fusible link I described above is a smaller gauge. Thank you for the clarification.

[Unsub]

I am curious to know why a fusible link ( a length of wire) is used rather than a fuse holder and fuse or a manual reset circuit breaker. My E Z wiring kit specifies there is no warranty if the link is not used so of course I have used it but if it should fail it is in a PIA place to get to to repair or replace. As previously said I am just curious as to why such a system is used.

[VetteVet]

Here's some reasons.

http://www.madelectrical.com/catalog/fusible-link.shtml

[Unsub]

Originally Posted by VetteVet

Here's some reasons.

http://www.madelectrical.com/catalog/fusible-link.shtml

Thank you for that it has cleared up my lack of understanding. The internet is such a wonderful thing especially when you have access to people willing to share there experience, it is greatly appreciated.

[Foot Stomper]

Searched the forum for purple wire and behold, here I find a great thread!

Perhaps you guys could help me on this?

I recently aquired a 1955 Cameo and all wiring seems to be factory and not tampered with. I've got a (disconnected) purple wire coming out of firewall grommet on passenger side that is hanging down near starter. Where should it be connected to?

As I am chasing gremlins in the truck, I haven't yet discovered (nor really tried looking) what this wire provides power to. As far as FL, I will buy one today and install if you guys says that's what's required. If I've read this thread correctly, I need one 4 sizes smaller. I believe this wire is 16 ga so will buy a 12 ga FL.

TIA

[VetteVet]

This might be the wire that activates the starter solenoid. On the newer trucks The solenoid uses a 12 gauge purple wire and the solenoid also kicks the starter gear into the flywheel. Yours might use a worm gear to do that so it wouldn't need as large a wire for the solenoid.

Check the purple wire for 12 volts with the key off, then check it with the key on. If neither way shows voltage then have a partner turn the key to START and check it. If you get voltage then it is the solenoid wire and will go to one of the small terminals on the solenoid.

You can answer in the other thread you started. I replied there to your post.

[Foot Stomper]

Thanks Vett
I put the ameter gauge on it today and had only 5 or 6 miliamps with ignition on and off.
Truck starts with key on with a "foot stomp".

Noticed headlights aren't working today but that could be a completely different gremlin but thought it worth mentioning...