Horn Wiring Help Needed (switch between two horns)

Installed an air horn and want to install a SPDT switch to toggle between the stock horn and the new air horn. So now I need to tap into the horn trigger wire, run it to the new SPDT switch and connect back to the horn trigger wire.

This is so I can use the steering wheel horn button to control each set of horns separately. Position 1 on the SPDT will trigger the stock horns only. Likewise, position 2 will trigger only the air horns using the steering wheel horn button.

I know I can tap the red / green horn trigger wire on the steering column, but that's a pretty congested area, and since this next goes through the body ECU, I think it's best to tap in downstream of that.

So where to tap into downstream of the ECU? Best spot would be at or near the horns by the radiator, but it looks like the two horns each go to a separate harness. Attached image is for a 2003, but I assume my '04 is the same. F5 and H10 are the two stock horns and their harnesses. Has anyone explored the exact point where the harnesses combine? I hate to do surgery on delicate parts like wiring unless I really have to.

Where else can I access the horn trigger wire? Has anyone else done this?
Guidance appreciated.
Many thanks,
--Paul

 

I don't understand what you are trying to do? you only need one horn

if you want two separate horns then leave stock alone and run a power wire from an accessary terminal in the fuse box or directly to the battery and run it through and inline fuse then inside the truck to a dash mounted switch then back out to the air horn.

if you have an air horn that needs more power then stock wiring can handle (as most big air horns do) then connect the air horn to a horn relay switch ($4 at any auto store) and run a power wire from an accessary terminal in the fuse box or directly to the battery and run it through and inline fuse then back to the air horn relay contact. the horn plugs on the opposite contact so the steering wheel horn powers the relay (very low power draw) and the larger power draw needed for the horn comes straight from the battery through the relay contacts as a separate power source.

 

Keakar,
my air horn and compressor are all wired up using a relay. Currently the solenoid is triggered by the stock horn switch and wiring. Works great.

What I'd like to do is toggle between the stock and the new air horn systems. The air horn is so insanely loud, that sometimes (like when my wife borrows the Tacoma) it makes sense to have the horn button trigger the stock horn only.

Thus, I need to find the part of the wiring harness where I can can add a SPDT switch to toggle between the two.

Thanks!
--Paul

 

I don't agree with having an obnoxiously loud air horn, but it sounds like a fun project to be able to switch between the 2 horns.

You need to get a manual that has the wiring diagram for your truck. Then follow the color-coded wire from the steering wheel. It should go to a relay, then tap into that wire just before the relay. Not sure where the relay is located.

 

ok well then its simple and all you need is a piece of old extension cord and a 3 pin on/on toggle switch so one side always has power.

mount the toggle switch under or in the dash and run the wire through firewall and out to the air horns.

hook one wire to the power wire for the air horn and then that sends power to the switch and hook the one wire to regular horn and the other to the air horn.

use extension cord because its heavy gage wire and its well protected from abrasions, heat, or vibration.

if you don't need an "internal" switch in the cab, then just put the switch under the hood and when you want the air horn just pop the hood and flip the switch

"short answer" put your switch between power wire to the air horn after the horn relay and before the horn

 

Any update on this project? I have a similar project that I plan on doing.