Eco-BEAST 28

Here is the problem I'm running into. My factory horns died a long time ago and since then I've replaced it with 2 aftermarket horns that add some more volume and tone. The problem I was running into was the 20A fuse for my truck (Fuse Box Spot 24 IIRC for my 2011 FX4) was blowing because of the added load. In order to fix it i simply swapped it out with a 30A fuse. I understand that the electronics are set the way they are for good reason so am I putting my truck and BCM in danger by running this high of a fuse in a spot meant for 20A? Any help or guidance would be much appreciated.

Tothemax

All depends on load and wire gauge. I am not sure what size wire feeds the horns?

4Stroke

Yes

Do happy short beeps, not long you f'n @$$O beeps and you may avoid starting a fire.

Eco-BEAST 28

Pretty sure it's just 16 gauge wire

TimelessR1

Fuses ratings are chosen based on wire gauge and length of run, not the load at the end of the wire. If it was me.. I'd put the 20 amp back in, get a relay and let your Oem horn wire trigger the relay, and use power directly from the battery with a correct sized fuse based on what wire gauge you use and how long that wire is

Eco-BEAST 28

I went and switched the fuse back to a 20 amp, but since I'm an electrical moron I have no idea what you mean by using a relay to let the OEM wire trigger the relay

johnday in BFE

iTrader: (1)

My 2012 owners manual says it's fuse #22. Regardless, using a higher capacity fuse than 20 amp, in a circuit designed for 20 amp, is a huge NO. Never increase fuse capacity, this includes your house as well. Many fires have started this way.
A 20 amp fuse is there to protect a circuit with a #12 wire, a 30 amp fuse protects a #10 wire. Smaller wire size numerically denotes a larger physical size, hence more capacity.
I think I'd be finding a horn setup that requires less than 20 amps to work.
I know what the manual says, but wow, 20 amp for just the horn? That's quite a bit of power.

Possibly you a chaffed wire somewhere?

Great white

iTrader: (1)

It's easy stuff.

Your original horn wire will only trigger the relay, which typically draws 1A or less. The relay provides power to the accessory.

A relay is just a component that has a little electromagnetic coil in it and a switch. When you power the coil, it pulls the switch (ie: contacts) closed. Since your horn circuit is now only powering the coil, it only sees a 1A (or less) draw. The contacts in the relay directs the power to the accessory. Since the relay is remote, it can be placed closer the the battery and you can run wire suitable for 30A (or more). Since you're only talking about less than 5' run of wire to the relay and horns, 18 gauge wire is sufficient.

Your original horn circuit actually has a relay in it that does the same thing, it's just that it's only rated for 20A, which doesn't work for you. You also can't just change it out. The system is only designed for a maximum of 20A, so you're stuck with it. OEM's are notorious for using the absolute bare minimum wire gauge (or less) for things, mostly to save money as copper is very expensive. The less they use, the more profit they make.

You can buy a 30A relay and all is good:



Don't worry if all you can find is a 40A, just make sure you don't get a 20A. All the amperage rating on the relay means is it maximum current it's rated for. More is fine, less is not. Especially since you know 20A is not enough for your horns.

Same as relays that have 5 blades instead of 4. both work. the 5th blade is just a normally closed position (you want the normally open blade for your horns).

Like so for 5 blade:



You would use 87 for your horns, 87a would be left empty. You're better off with a 4 blade though, as blade 87a would be hot at all times when not using the horn. It's pretty unlikely, but should you be working and touch it with a wrench or screwdriver, you'd get a spark/short.

Here's a typical circuit that would work for you:



Where the switch is in the diagram, you would use the original wire that goes to the horns. Put the relay in a relatively dry spot under the hood. Where the lights are in the diagram is where you would hook up your aftermarket horns.

TimelessR1

^ this

Thanks Great White for explaining that!! That took patience ;-)

Spiky

They need to be chosen on both.