stock power wire

[AcampoDave]

Would it be wise to install a breaker or a fuse on the unprotected main power lead from the battery to the horn relay? I was just wondering if a 30 amp breaker would be good call.

[ray_mcavoy]

Yes, adding some protection to that wire would be a good idea.

GM added a fusible link on the battery end of that wire starting in 67 and I recommend doing the same for these years. I prefer fusible links over fuses or circuit breakers for this type of application because they are more compact (they just splice directly inline with the wire they're protecting). Obviously, they are not as easy to replace as a fuse (or resetting a circuit breaker). But if your wiring is in good condition, they're not something you'll have to replace on a regular basis either. The fusible link should only blow in the event of a major overload or a dead short to ground.

If you decide to use a fusible link, the rule of thumb is to size them 4 wire gauge numbers smaller than the wire they're protecting. So for a stock 12ga wire, use a 16ga fusible link. Also, the fusible link wire should be about 6 to 9 inches long.

[AcampoDave]

Ray, thanks for your reply. I have a question about the fusible link though. If I downsize by 4 numbers on that wire wouldn't it be a restriction to the flow of current. Kinda like putting a section of 1" pipe in a 3" exhaust. Maybe a poor analogy, but you get what I mean anyway.

[ray_mcavoy]

You're welcome!

Yes, I can understand your concern about the small size wire creating a restriction. However, when it comes to wire size and current carrying capacity, you also have to take the length of the wire into consideration. In the case of a fusible link, the length is purposely kept short enough to not add a considerable amount of resistance (restriction to current flow) to the circuit. That's why it's recommended not to make a fusible link any longer than 9 inches.

As a comparison, take a look at a regular automotive fuse. Notice how tiny the fusible metal strip or wire inside is in relation to the size of the wire it's protecting. But also notice how it's length is very short. Again, it's that short length that is the key to keeping the resistance (restriction) very low.

[AcampoDave]

Very good. I get it now. That makes sense when you compare it to a fuse. I guess I'm gonna do it then.

[R_W]

x2 for fusible link. I got several gages from Autozone, think I had to order it though. Fusible link is safest and easiest way to protect from a hard short that can cause real problems.