1971 Cutlass convertible. What gage wire should be running from the battery to the Horn relay junction block? Also what gage from the Junction block to the Alternator. I'd like to install a fuse in the line from the battery to the junction block. Would a 60 amp be large enough at that spot? Car is standard shape & accessories.

 

Go the electrical forum on this site, find the 1971 wiring diagram sticky and you can look it up. Buy the 1971 CSM which contains the color wiring diagram and much more useful information.

 

Thank you. I have an enlarged copy of that diagram in my files & printed out on 4 sheets poster size. It indicates #10 wire battery to junction block, but no size on the alternator output. #10 seems a bit low if you have a 100 amp alt & low battery. Just wondering what others think. I have a different diagram I bought on line showing a fuseable link in the battery to junction block line, but nowhere information on size. I have both Factory Service Manuals & didn't see it referenced. I actually want to use a maxi fuse, but again an seeking advice regarding size. Take Care.

 

There is no reason to put a fuse or fusible link in the wire that runs from the battery to the horn relay stud. The only fusible link at the horn relay stud is the wire that runs to the bulkhead connector.

The chart below will tell you the load carrying capacity by wire ga and length.

 

My three 1970 Cutlasses had 10 ga wire from alternator to horn relay junction block and junction block to battery. The small, factory-size wiring was designed to limit charging amps to extend the life of the wet battery. It will work well even with your higher-output alternator and will continue to protect a wet battery from excess charge.

If you have a pure-lead AGM battery and plan on that for the future, you can up-size alternator-to-junction-block and junction-block-to-battery wires to suit the output of your alternator. The pure-lead AGM battery will effectively absorb whatever charging amps the alternator sends down the wire.

If you have an AGM but it does not specifically state "PURE LEAD" then you must limit the charge amps by retaining the factory wiring.

If you are set on installing a fuse, I would fuse the junction-block-to-battery at 200% of wire capacity because it is such a critical load. Audio fuses are made in these large sizes. A blown fuse in this location could shut down the entire car. Better to have warm wires and still be able to drive to a repair shop than be stranded. You would still be protected against a dead short.

For complete background information on battery types and charging, refer to article on pages 18 to 21 in the February 2022 Journey With Olds magazine.

 

Thank you very much for the excellent advice.