[bhill86]

You would think. I’m not an electrical engineer but the connection may be a point of resistance causing heat buildup. Maybe made worse being under hood. My original connector was also melted. I still have it somewhere. I was missing the remainder going to the alternator.

You’re correct on 12ga though. Below I attached the diagram from my manual. The A/C diagram doesn’t designate the fusible link but the chassis electrical does. Both show 18ga.

[i4abuygto]

Thanks Bhill86,
You have been very helpful with my introduction to the 79 TA- The manuals have helped alot.
I was reading about fusible link wires and they are supposed to be 4 gauge sizes below the main wire. That would make it a 16 gauge fusible link wire. I found the original fusible link wire for my TA connected to the harness as shown on your diagram - looks to be an 18 gauge fusible wire. I found it connected to a cut wire in the relay harness that was buried under the hood. I ran a new 12 gauge wire from the alternator and attached the fusible link at the connector for the high speed fan feed wire going to the high speed fan relay. I believe I put the fusible link closer to the relay than stock harnesses so the circuit should be protected.
All speeds on the fan work great and the high speed really blows.
Now I am working on the vacuum feed for the AC controller and have found that the vacuum system under the hood is messed up.
No PCV valve or PCV line to the carb. No vacuum hooked up to the vacuum advance on the distributor.
So I will have to figure all that out this weekend.
Thanks for your help.
Mark

[bhill86]

Glad to be of help but two points to mention. I believe the length of the link is a factor in how much overload protection it offers, obviously also affected by the gauge, which is why you found a difference between the recommended link size vs what the factory installed.

The other thing is if you look, the factory located the link much closer to the alternator. That way the entire circuit is protected. I think I the way you have it with the link closer to the relay leaves the preceding part of the circuit vulnerable to overload and may be a fire hazard. Just something to consider.

As for your vacuum situation, the manual would also help. They really are invaluable when working on these cars.

[i4abuygto]

The other thing is if you look, the factory located the link much closer to the alternator. That way the entire circuit is protected. I think I the way you have it with the link closer to the relay leaves the preceding part of the circuit vulnerable to overload and may be a fire hazard. Just something to consider.

Great point - mostly I wired what I have to test- I will likely just put a fuse in the line from the alternator - I will shy to the light side with a 20 amp fuse.

[highway star]

Is this the fused wire coming off the alternator? I took this off a while back when I was re-routing wires, perhaps I should reinstall it? It had a 20A fuse in it. Thanks!

[burd]

I have a box of harness’s that was given to me, it a community freebie on my forum, if you need a wire or two, Leme know. I rob out of them all the time for people.

[bhill86]

Originally Posted by highway star

Is this the fused wire coming off the alternator? I took this off a while back when I was re-routing wires, perhaps I should reinstall it? It had a 20A fuse in it. Thanks!

No, the factory wire had a fusible link not a fuse

[highway star]

No, the factory wire had a fusible link not a fuse

Oh ok, I may have that link, is it a square rectangular link? Happen to have a picture of that “fusible link”? Much appreciated!

[i4abuygto]

I dont have a picture yet - it is like a regular wire but it is softer (less stiff coating) and the coating will have "fusible" or "fusible link" printed on it - if you search the internet under fusible wire it will have many examples of fusible link wire that can be purchased in variable lengths and gauge. I am not an expert - I only searched and found that the fusible link wire is recommended to be 4 gauge smaller than the main circuit wire (i.e. if it is a 12 gauge feed wire the fusible wire is recommended to be a 16 gauge fusible link wire).
The wire is designed to "melt away" to break the circuit in case of a short.

[highway star]

Is this the oem “fuse link”?? Thanks, Robert

[bhill86]

No, i4abuygto said it well. A fusible link is just a wire that is designed to fail safely rather than catastrophically like a typical wire. Google fusible links and you’ll see lots of examples with different connectors.

I’ll post an example below.

Also mods can feel free to delete if referencing another forum is frowned upon but if not here’s some info that may be helpful also….

https://www.78ta.com/HTAF/index.php?topic=40340.0

[highway star]

I did cut something out like my last pics & then connect just the wires back together. It was near the driver’s valve cover. 1978 T/A. Bought the car in original state.

[i4abuygto]

I did cut something out like my last pics & then connect just the wires back together. It was near the driver’s valve cover. 1978 T/A. Bought the car in original state.

I dont recognize the black piece but the cream color connector looks stock to the Trans Am -

I believe the print on the wire (in photo circled in red) is the fusible link print and that connector looks to be the connector for the fusible link attached to the 12 volt post on the alternator.

It is important that the high speed fan circuit be protected or wires could melt and fires could start.

I dont know these TAs and Firebirds like others on this forum - I am still learning - so other could confirm details.