Switch between stock horn and train horn

So after lots of research and testing I finally finished my install. I decided to write this post because I couldn’t really find one outlining exactly how to wire train horns the way I did…although it is very possible that I just couldn’t find the post. Anyways I wanted to be able to switch between my stock horn and train horns via an illuminated toggle switch and using my stock horn pad to sound the horns.

I am using PVC horns with a few modifications off of the famous dozzerboymiller plans, haha. They are tuned to the K3LA. I decided to run them off a 10 gallon air tank through 3/8" line into a 1/2" solenoid then into a 1/2" pvc manifold with 1/4" line to each horn.

Wiring everything was simple but I made it complicated in my head so hopefully this helps someone. All you need is a simple 3 prong illuminated toggle switch with ground, load, and hot prongs. The hot prong is connected to a 12v source (+ on battery) and the ground is obviously grounded. Next you need a 5 prong NO/NC relay with 30, 85, 86, 87, and 87a prongs (I believe a fuel pump relay is what I used). This relay works by having prongs 30 and 87a connected when it’s not energized, and upon energizing the relay prongs 30 and 87 then become connected, basically it acts as a switch from one to the other. So to wire everything up you connect the positive wire coming from you steering wheel to prong 30, the positive wire coming from the stock horn to prong 87a (this allows the stock horn circuit to basically stay the same) then you take the “positive” off the solenoid (there is no set positive/negative wires on the solenoid so just pick one and ground the other) and connect it to prong 87. Finally ground out prong 86 and connect the load wire from the illuminated switch to prong 85.

This will allow you to have an illuminated switch in you vehicle so when you flip it on it will light up so you know it’s on, in case someone tries to play a joke on you. When you flip the switch it will energize the relay switching it from your stock horns (when the switch is off) to your train horns (when the switch is on), allowing you to pick one or the other.

Hopefully this helps someone. Happy scaring the “poop” outta people by honking!

Welcome to the forums.

Welcome. I’ve seen those relay pin numbers before and someone told me it was a horn relay but I’m sure it can be used for many things.

Thanks! And yea that relay is used on a lot of things.

Hi Snowboarderr, I almost have the same setup on my horns. I wanted to be able to switch between the stock & airhorns on my steering wheel horn too. Not sure about other cars, but I figured out that using my rear window defogger switch, which lights up when on, worked PERFECTLY for this! It’s pretty fail-safe for switching between stock & airhorn with no WHOOPS, forgot it was on, nobody can play any tricks.
In my car, as I’m sure most cars are, the defogger switch only works with IGN ON, it’s only active for 5-10 minutes before automatically shutting off, and once the IGN is shut off, it’s off, must be pressed again to activate after IGN ON. This is where I spliced in my stock horn-to airhorn relay. So basically, just hit the defog, and she’s good to go, if i forget to switch off, it does it automatically after 10 mins or so. NO WAY your honking the airhorn unless you mean it!

That’s a pretty neat trick!
I guess having the rear defogger on for 10 minutes isn’t a terrible thing.

Not at all. I recently let my roommate drive my car to work while I did him a favor and replaced the radiator on his car (YAAY for me!):rolleyes:
He knows about my horn, but he had to call me to ask (for permission first), then how to engage it.
Sure, I told him how, why not. but be careful.:wink:

What would make my fuse on my stock horns blow if I did the same setup. It’s after I hit the switch to use my train horns

Weston, welcome to the forum.

Something is obviously drawing more current than the fuse can handle. Verify the current draw and fuse rating; otherwise, look for a short.

I’m wanting to use a 3 position switch for mine I have a 08 mega can I have two horns both have a separate power wire which one would I tap into thanks

you are talking about a 5 Pin Relay. :slight_smile: another use for this relay would also be to deactivate a car alarm system completely when the ignition is turned to the “ON” or “ACC” position. :slight_smile: I am also getting some Ideas on how to make a blow off valve for the my compressor, so when it kicks off, an electric valve opens up before the check valve and goes “Pssssh!” to bleed the pressure off of the compressor. A little something in the making :slight_smile:

You just need a SPDT (single pole dual throw) switch or relay. Basically it will let you select one circuit over another. This should help you …