There's one problem with running to the horn relay, it's "hot" all of the time, even with the car off. Most people want switched accessories so they turn off when the car is not running to prevent battery run-down.
I suppose you could run to the horn relay, but remember, the horn relay junction is ALWAYS hot, it is not switched.
Yes, always use a fuse, even if it seems redudant. The only protection the horn relay circuit that feeds a lot of the car is the fusible link found off of the (+)terminal of the battery. It takes a lot of juice for this to melt so install a fuse on "add on lines".
Now, I stated in my original post (and about every other post) to run things right to the battery. Here's why:
1) As well made as vintage iron is, GM still was "cheating" a bit and under-sized some wires. The horn relay is already bogged-down with enough current draw--the more factory options you have, the more heavily this junction is taxed with current.
2) Age comes into play. 30+ years makes wiring/junctions/splices weak and corroded. Something that is connected so-so will definely crap-out under more load.
3) Troubleshooting. Much easier when you have your "own" wires to suspect or rule-out. When you combine factory and add-ons, it can be a tough call on what went wrong if something major would happen--i.e. whole vehicle goes dead.
That's why I suggest battery (+) terminal add-ons. Use a fuse though! Dead shorts off the battery are devistating to electrical systems. Also when you use the battery terminal you know you have the "best" connection possible (if you made tight connector connections and used a CLEAN battery terminal). Your new circuit has power without splice, after splice, after junction, etc.
Thank you mister Top, or is it ok to call you copper. Just a jokin. I am looking forward to Sat. so I can build one of the devices you diagramed. I usually shy away from electricity. You are one of the people that make this a great site watch. Thanks again Edd
Painless Wiring makes several fuse blocks with both switched and constantly hot terminals that are fused. You can get them through "Jegs" if you get the part number of the one you want from Painless Wiring and save some money.
Redrum (or Mike)
68 Corvette - 383 CI 427 HP
69 SS Chevelle being updated to Pro-Touring
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