Use a 5-pin SPDT relay and a toggle switch so the steering wheel can honk either the stock horn or your train horns — one at a time.
What you need: SPDT 5-pin relay (10A minimum — not supplied by HornBlasters), toggle switch, wire strippers, voltage meter, and a solid chassis ground
Overview
1
Know what you’re getting into
Setting the horns up on the steering is a challenge in itself. Setting it up so that both horns are separate can be a challenge and we would not recommend following this article if the steps below are intimidating to you. Our authorized installers can help you out with setting this up if needed. Our installer locator can be found here.
Get Started
This article assumes that the rest of your kit has been installed and you are just wiring the horn up. If you are not at this step yet, please view the previous installation articles here.
2
Items required
SPDT Relay (must be a 5-pin relay, 10A minimum). HornBlasters does not supply this part. This relay must be sourced.
SPDT relay wiring overview for switching between two horns.
3
Locate the OEM horn
Start by locating the OEM horn. On most modern vehicles, the horn is located behind the front grille area, directly ahead or to the side of the radiator. Check out the image below.
You don’t have to remove the bumper in most cases to access the OEM horns, but it does in some cases make your life easier.
Factory horns are typically ahead of or beside the radiator.
4
Find the horn connector
Once you have located your stock horn, take a look around for a small connector going into the horn itself. These connectors almost always have two wires coming out of them. The image below gives you an idea as to what to look for.
Look for the two-wire connector at the horn.
5
Cut the OEM positive wire
This is where the install gets a bit tricky. To make this work, the positive wire to the OEM horn must be cut. If you are unsure as to which is the positive wire, do not cut anything. We recommend starting at the connector and going back ~6–8" so you have plenty of wire to work with. Cut the wire in half, and strip each end. If you’re unable to tell which wire is the positive wire, you can use a voltage meter to test both wires.
Do not cut until you are sure which lead is positive.
The Relay
The Single-Pole Double Throw relay you are working with has five posts on the bottom.
6
Understand the five posts
This relay is very similar to the 4-pin relays we use with some of our kits. The added post ‘87A’ is used for a second accessory. These relays are designed to switch between two circuits, when on or off. You will set this up so that one circuit is for the regular stock horn and the other is for the train horns. Both can be honked with the steering wheel, but only one at a time will honk.
SPDT pin layout — note the added 87A post.
7
Wire the relay posts
87: Connect the wire from OEM horn (the short wire lead we cut earlier FROM the horn itself. Route this to pin 87).
87A: Connect the red wire from our solenoid valve to this terminal.
30: Connect this terminal to the side of the OEM horn wire that comes from the steering wheel (the wire that is NOT coming off the horn itself).
86: Connect this post to the toggle switch you plan to use to switch between the two horns.
85: Route this post to the frame of the vehicle as a ground.
The steering wheel will be used to honk each horn, and the toggle switch allows you to switch between the two. When the vehicle is off, the horns will still honk but the compressor will not run.
Steering wheel trigger, toggle switch, OEM horn, and solenoid valve.
Next
Turn horns on/off at the steering wheel using an upfitter switch.