Wire from battery to horn relay - Team Camaro Tech
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post #1 of 13 (permalink) Old Jan 20th, 15, 09:38 AM Thread Starter
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Wire from battery to horn relay

Can anyone tell me what gauge wire the main lead which runs from the battery to the horn relay is in a '69 ? The horn relay acts as junction block for the car's entire electrical system. If I remember right, what ever size it is, considering everything aside from the starter is run off this lead, it's smaller then what really should be in the car based on the potential load. If I run a new lead, what gauge should it be? Thanks!

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post #2 of 13 (permalink) Old Jan 20th, 15, 10:01 AM
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Re: Wire from battery to horn relay

The wire you're talking about is a 10ga. It runs from the junction block by the battery to the main splice in the front light harness and from there to the horn relay. From the batt+ to the junction block is a 14ga fusible link.

The vast majority of these cars had 37ish amp alternators and the wiring was sufficient for the equipment available at the time


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post #3 of 13 (permalink) Old Jan 20th, 15, 10:06 AM
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Re: Wire from battery to horn relay

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Originally Posted by JohnnyD View Post
Can anyone tell me what gauge wire the main lead which runs from the battery to the horn relay is in a '69 ? The horn relay acts as junction block for the car's entire electrical system. If I remember right, what ever size it is, considering everything aside from the starter is run off this lead, it's smaller then what really should be in the car based on the potential load. If I run a new lead, what gauge should it be? Thanks!
The stock battery wire will work just fine.
The only current that goes through the wire from the horn relay to the battery is the current necessary to start the car, i.e. the ignition system and possibly a fuel pump. All the other current from the battery heads to the starter directly.
After you have started the car, the battery becomes a load on the system, and only the current necessary to recharge the battery goes through the wire. All other current used in the car comes from the horn relay, the highest voltage point.

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post #4 of 13 (permalink) Old Jan 20th, 15, 12:01 PM Thread Starter
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Re: Wire from battery to horn relay

Thanks for the responses. The high amperage starting current for starter motor goes directly from the battery to the starter via the solenoid. Only the trigger current for the solenoid (low amperage) goes to the solenoid via the horn relay circuit. So back to my question, with the present day demands such as stereo amps, higher amperage head lights, cooling fans being installed latter this week ... Are any upgrades to the wiring from the battery to the junction block/horn relay necessary? Thanks everyone.

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post #5 of 13 (permalink) Old Jan 20th, 15, 12:10 PM
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Re: Wire from battery to horn relay

Depends on how the current from your alternator is getting to the load location for the car which should be the horn relay. The entire length of the cable or wire that goes from the alternator to that load location needs to be of a large enough gauge/size to handle the maximum current your electrical system could place on it.

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post #6 of 13 (permalink) Old Jan 20th, 15, 12:14 PM
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Re: Wire from battery to horn relay

With the stock harness you don't have the added circuits needed.

I would suggest you add a fuse block then pull the added circuits you need for fans, etc off of it.

Something like this with a couple switched hots, a relay and a circuit breaker

http://www.summitracing.com/parts/prf-70107/overview/

or This if you just want 12 hots

http://www.summitracing.com/parts/aww-500383/overview/

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post #7 of 13 (permalink) Old Jan 20th, 15, 12:32 PM
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Re: Wire from battery to horn relay

You can piggyback an additional wire from the alternator output stud to the horn relay bus if that's where you attach your fans w/o digging into the harness. You'll have to figure out the wire size based on current that the new fans draw. Also a good place to add headlight relays.


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post #8 of 13 (permalink) Old Jan 20th, 15, 12:40 PM
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Re: Wire from battery to horn relay

To choose an adequate wire gauge, determine the amp draw (amperage) that the wire circuit will carry. Then measure the distance that the wire will travel (length) including the length of the return to ground (the ground wire running to the chassis or back to a ground block or battery. Using these two numbers, Amps and length, locate the nearest gauge value in chart below. For 6 volt automotive systems typically a wire gauge 2 sizes larger than what is shown should be used.



Amps
@ 12 Volts LENGTH OF WIRE
American Wire Gauge (AWG)
3' 5' 7' 10' 15' 20' 25'
0 to 1 18 18 18 18 18 18 18
1.5 18 18 18 18 18 18 18
2 18 18 18 18 18 18 18
3 18 18 18 18 18 18 18
4 18 18 18 18 18 18 18
5 18 18 18 18 18 18 18
6 18 18 18 18 18 18 16
7 18 18 18 18 18 18 16
8 18 18 18 18 18 16 16
10 18 18 18 18 16 16 14
11 18 18 18 18 16 16 14
12 18 18 18 18 16 16 14
15 18 18 18 18 14 14 12
18 18 18 16 16 14 14 12
20 18 18 16 16 14 12 10
22 18 18 16 14 12 12 10
24 18 18 16 14 12 12 10
30 18 16 14 12 10 10 10
36 16 14 14 12 10 10 10
40 16 14 12 12 10 10 8
50 16 14 12 10 10 10 8
100 12 12 10 10 6 6 4
150 10 10 8 8 4 4 2
200 10 8 8 6 4 4 2



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post #9 of 13 (permalink) Old Jan 20th, 15, 01:31 PM
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Re: Wire from battery to horn relay

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Originally Posted by JohnnyD View Post
Are any upgrades to the wiring from the battery to the junction block/horn relay necessary?
In a word - no. As previously noted, this wire is used only to start the car and recharge the battery. If you were starting the car and recharging the battery before, it will still work now. All added electrical load should be wired to the main power distribution point and appropriate wiring changes made there.

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post #10 of 13 (permalink) Old Jan 20th, 15, 03:55 PM
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Re: Wire from battery to horn relay

Courtesy of PozziRacing Thanks Dave.


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post #11 of 13 (permalink) Old Jan 21st, 15, 09:12 AM Thread Starter
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Re: Wire from battery to horn relay

Again, thanks for the responses. Looking at the wiring diagram, I'm a little confused why #14 is used between the battery and the junction block when #10 is used between the block and the horn relay. Can someone enlighten me please

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post #12 of 13 (permalink) Old Jan 21st, 15, 09:55 AM
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Re: Wire from battery to horn relay

The way I understand it is fusible links need to be two wire sizes smaller than the wire they are attached to. If it's a 10 gauge, then a 14 gauge would be used. If it was a 12 gauge, then a 16 gauge fusible link would be used.

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post #13 of 13 (permalink) Old Jan 21st, 15, 09:57 AM
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Re: Wire from battery to horn relay

Quote:
Originally Posted by DOUG G View Post
Courtesy of PozziRacing Thanks Dave.

Quote:
Originally Posted by JohnnyD View Post
Again, thanks for the responses. Looking at the wiring diagram, I'm a little confused why #14 is used between the battery and the junction block when #10 is used between the block and the horn relay. Can someone enlighten me please
the #14 is the fusible link to protect the #10

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