Horns blowing fuses

[EastYorkStang 63]

I keep blowing 20 amp fuses for the horns on my 1970. Any ideas on what to look for? I have two stock horns. It's supposed to be a 20 amp fuse but they only last once.

[foothilltom 33]

My advice: use your horn in emergencies only. :)

 

Seriously, you have a short in your horn circuit. You'll blow a fuse every time and you don't want to keep increasing the size of the fuse unless you want to melt something or start a fire.

 

Diagnosing a short is kind of a pain, but if you approach it methodically, you can do it. You'll want to get used to using a multi-meter (one that measures resistance as well as voltage). Basically, you're looking for a low-resistance situation that, for example, could be caused by a horn wire exposed and grounding against the frame.

 

Fortunately, the horn circuit is pretty dang simple. You could also try disconnecting one horn at a time and seeing if this eliminates the problem, but you'll go through several fuses along the way.

 

There are a few things to suspect:

 

* Short in your actual horn switch (below the wheel)

* Short in your wheel hub (that activates the switch)

* Short in one of the wires to the horns (suspect those near sharp corners)

* Short in the horns themselves

 

You can test each of these circuits with your multi-meter. I can provide more info later if you need it. Get a wiring diagram if you can't trace the wires back from the horns.

 

Good luck.

Tom

[EastYorkStang 63]

I'm well used to a multimeter. How would I eliminate each step? If I run a power jumper to the fuse to trip the horn, would this isolate the column and button? Or unplug each horn individually?

[foothilltom 33]

Here's a really good YouTube video that shows a strategy for locating a short. He uses a circuit breaker wired across the fuse panel which is pretty cool (instead of just popping fuse after fuse). After that he's just "dividing and conquering" by disconnecting convenient points in the circuit along the way.

 

I think this is a pretty intuitive approach. Try it out...the example in the vid is a short when activating the horn!

 

Tom