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Hi -
On my '79 Alfetta I'm about to install a headlight relay as first in what will likely be a series of relay installs, w/ help from Daniel Stern. With my battery in the trunk, I think I want to take the feed off the starter end of the battery + cable. Novice question here, I am wondering how exactly that works? In this picture below, I THINK that's the red cable coming in at the top left of the frame. Would the headlight feed be another ring connector coming off where this one connects, or spliced into it somehow?

Another option, based on this post, if I understand it right, would be to run the power from what appears to be my car's version of the "power distribution terminal" on the left side of the engine bay - also pictured below - though mine appears to have two wires in and one out to the alternator, so I don't know that it's doing the same thing as the car in that post. Thanks for any suggestions.

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Either place - the battery or the power distribution terminal - will work. Electrically they are the same; I would bet that the other end of one of those heavy, red wires coming off the distribution terminal is the red wire you see connected to the starter.

A third alternative would be the stud on the back of the alternator. The place where the heavy, red wire to the the distribution terminal originates.

If it were me, I would be inclined to chose the power distribution terminal (or alternator). Here's why:

- 99.9% of the time when the headlights are on, their current is coming from the alternator, not the battery. The run from the alternator to the distribution terminal is shorter, so you'll have less voltage drop. The difference is probably only a few millivolts, but aesthetically, it makes sense to minimize the length of high-current wiring.

- You'll probably put your relays on the left fenderwell, since the existing headlight wires, which you'll need to splice into, run through that area.

- The distribution terminal is just easier to get at than the starter.

Would the headlight feed be another ring connector coming off where this one connects, or spliced into it somehow?
If you do decide to connect at the starter, it would be a LOT simpler to crimp a ring lug onto the wire going to the headlight relays and add it to the stud that holds the existing red wire and the heavy black lead to the battery. Splicing into that heavy-gauge wire would be messy.

Be sure to put a fuse between the power source and the relays!
 
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I used the block on the left fender, mainly for better access. Access to mount relays and to the headlight wiring harness.
 

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Discussion Starter #4
Thanks Jay, super helpful!

Either place - the battery or the power distribution terminal - will work. Electrically they are the same; I would bet that the other end of one of those heavy, red wires coming off the distribution terminal is the red wire you see connected to the starter.

If it were me, I would be inclined to chose the power distribution terminal. Here's why:

- 99.9% of the time when the headlights are on, their current is coming from the alternator, not the battery. The run from the alternator to the distribution terminal is shorter, so you'll have less voltage drop. The difference is probably only a few millivolts, but aesthetically, it makes sense to minimize the length of high-current wiring.

- You'll probably put your relays on the left fenderwell, since the existing headlight wires, which you'll need to splice into, run through that area.

- The distribution terminal is just easier to get at than the starter.



If you do decide to connect at the starter, it would be a LOT simpler to crimp a ring lug onto the wire going to the headlight relays and add it to the stud that holds the existing red wire and the heavy black lead to the battery. Splicing into that heavy-gauge wire would be messy.

Be sure to put a fuse between the power source and the relays!
 

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Discussion Starter #5
I used the block on the left fender, mainly for better access. Access to mount relays and to the headlight wiring harness.
I had missed this thread in my earlier research. Thanks for the helpful pictures there!
 

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Not to stray from the thread topic, but while you're working there above the alternator, run a second 8 gage red wire from the alternator post (where the one is now), right alongside the existing red wire, and up to the junction block on the fender. Your battery will thank you for it.
 
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Discussion Starter #7
Not to stray from the thread topic, but while you're working there above the alternator, run a second 8 gage red wire from the alternator post (where the one is now), right alongside the existing red wire, and up to the junction block on the fender. Your battery will thank you for it.
Thanks Alfaloco - that sounds easy. What does that do?
 

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It is easy, and it provides a new uncorroded main output wire to battery feed from the alternator. Over time, these big wires can corrode internally, between the crimped lug and the wire strands, resulting in higher and higher resistance. This internal corrosion is not visible but still results in voltage drop.
 

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Also slightly off topic but some more advice, assuming the same basic wiring as in the GTV6, in addition to headlight relays, one across the ignition switch to starter solenoid, you can loose a few volts across the thin wiring and the old, high resistance switches. Clean up all the earths you can find, even using wet and dry to get clean metal and use dielectric grease to prevent later corrosion.
 

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It is easy, and it provides a new uncorroded main output wire to battery feed from the alternator. Over time, these big wires can corrode internally, between the crimped lug and the wire strands, resulting in higher and higher resistance. This internal corrosion is not visible but still results in voltage drop.
So basically just run another wire, parallel to the existing one, between alternator battery feed and junction block? What about just replacing the existing one with a new one?
 

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So basically just run another wire, parallel to the existing one, between alternator battery feed and junction block? What about just replacing the existing one with a new one?
Hi there Sam-- Why remove the original red wire when you can simply augment that wire lead? Unless it's visibly corroded and green inside the end terminals. More than likely it's still carrying voltage, the second wire simply reinforces its capacity to charge the battery. When my son and I did this upgrade, we simply wrapped the new 10 gage wire around the old one, all the way up to the junction block, in a spiral.
 

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Hi there Sam-- Why remove the original red wire when you can simply augment that wire lead? Unless it's visibly corroded and green inside the end terminals. More than likely it's still carrying voltage, the second wire simply reinforces its capacity to charge the battery. When my son and I did this upgrade, we simply wrapped the new 10 gage wire around the old one, all the way up to the junction block, in a spiral.
More is more... or, in this case less (resistance) is more :)
 

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Sorry if this is a silly question but why three relays? I would have thought either two or four
Regards Geoff
 

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Sorry if this is a silly question but why three relays? I would have thought either two or four
Regards Geoff
In my case I used two relays for high beams as on my car that triggers four lights to be on. The relays I used were 30 amp which is a bit under rated for all four on at once. At least that was my reasoning....
 

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I’m using four on my 76. Also, take the opportunity to run thicker gauge wire up to the headlights. Remove all chances for failure.
Btw, three relays is prob OK per Carson’s note. Again, wire is just as important as relays...
 

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Hi -
On my '79 Alfetta I'm about to install a headlight relay as first in what will likely be a series of relay installs, w/ help from Daniel Stern. With my battery in the trunk, I think I want to take the feed off the starter end of the battery + cable. Novice question here, I am wondering how exactly that works? In this picture below, I THINK that's the red cable coming in at the top left of the frame. Would the headlight feed be another ring connector coming off where this one connects, or spliced into it somehow?

Another option, based on this post, if I understand it right, would be to run the power from what appears to be my car's version of the "power distribution terminal" on the left side of the engine bay - also pictured below - though mine appears to have two wires in and one out to the alternator, so I don't know that it's doing the same thing as the car in that post. Thanks for any suggestions.

View attachment 1676725

View attachment 1676726
 

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Sorry if this is a silly question but why three relays? I would have thought either two or four
Regards Geoff
On the super we have 4 headlamps. The large ones have high and low beams. So, a total of 6 bulb filaments.
One relay feeds the two low beams. The other two split the high beams - 2 on the right, 2 on the left.
 
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