Air horn toggle wiring

[Strahan]

I honked my hatch's horn last weekend and realized how wimpy it is. I figured I'd get an air horn instead. However, I don't want to be pulling up to a friend's house late at night and have to honk my air horn to let them know I'm there, I'd prefer the wimpy stocker then. So I figured I'd mount a momentary switch somewhere that when pressed makes the steering wheel horn buttons switch to the stock horn, and when the switch is open it defaults to the air horns.

I originally made this wiring diagram (http://www.nischan.com/crap/diagram2.jpg) but I don't think trying to run the air horn compressor off the stock +12v horn trigger wire is a good idea.

So I made a new diagram (http://www.nischan.com/crap/diagram1.jpg) using one relay to monitor the stock +12v that goes hot when the horn button is pressed and when it sees that hot, sends a heavier gauge fused power to a second relay that handles the horn switching. The momentary switch will trigger that second relay. At rest, input power connects to the air horns, and when the relay is energized it switches input power to the stock horn.

Just wanted to post it and see if it looks good, or if there is a more efficient way.

[Strahan]

..and PS, anyone have a good source for cheap Bosch relays with the cooresponding plugs/pigtails?

PPS, Ideally I'd like to have the momentary mounted on the inverse side of the steering wheel from the upper left horn button. I haven't checked to see if it would be feasable yet though. Is it possible to send a wire down from the steering wheel that won't bind up when the wheel is turned?

[Hazwan]

Look about right but I thought the horn button from the steering wheel is negative?

Also wouldn't it makes sense to use toggle switch instead?

[Strahan]

I dunno what comes from the wheel, I was just gonna grab the trigger from the wire in the engine bay that goes to the horn. My car is in the shop at the moment, so I haven't been able to investigate the stock wiring yet so this is going by assumptions of what is there.

As for why I chose momentary, it's because I will only need the stock horn on rare occasions and it'd be annoying to forget and leave it switched on stock.

[Hazwan]

Ah that makes sense. If you're using toggle switch theres no need for the 1st relay but since you've opted for the momentary thinggy I guess thats okay.

[Dr_Snooz]

Check the horn switch contacts in your steering wheel. They can get corroded and make your horn sound pretty feeble. Clean them up with emory cloth and you will notice a big difference.

[2ndGenGuy]

Hazwan is right, the horn buttons do in-fact ground the circuit. So you'll need a little modification at the first relay. The second switch you have set up, you'll need a special relay for that jazz. A standard relay won't do the trick, and only completes the circuit. The two places where each horn is hooked up are actually the same connection. I dig the wiring diagram though with the photos and everything! :thumbup:

[Strahan]

Yea, I guess the diagram is misleading. I'm not tapping the actual horn button. The relays and the air horns are going to be in the engine bay already, so I'm disconnecting power from the stock horn and using that +12v to the horn as the trigger, since it obviously cannot go hot unless the horn is pressed. That way I don't have to fish a seperate horn trigger from the cabin.

Regarding the relay, I'm using SPDT. When the relay coil is at rest, 30 and 87a are connected. When it's energized, 30 and 87 are connected. 87 and 87a are not normally connected in a SPDT unless you jumper them.

[Blkblurr]

If I were going to do what you are, I would make the momentary button work the original horn and the steering wheel work the air horn. No relays needed at all.

[Strahan]

I finally got around to doing this today:

http://www.nischan.com/crap/airhorn.jpg

Works great. Only difference was I used a negative switching system rather than positive. Air horns work best/loudest with clean power so I gave it a direct fused line to the battery. Reading my old post I realized I wired it backwards today, heh. Right now it defaults to the stock horn and the airhorns are foot operated. I suppose it would be better with air horns default.

I toggle the horns with this switch in the dead pedal:

http://www.nischan.com/crap/airhorn2.jpg

Had to buy a new drill with a 1/2" shank to make the hole, couldn't find a 5/8" drill bit in 3/8" shank hehe. I am also just running one horn right now. I couldn't find alot of room for both, so I just used the deeper tone one. I may buy some extra hose and mount the other to the firewall, but also I figure splitting the air between two horns will reduce the loudness most likely.


When I was working on it today I went to put it on ramps to access the horn easier and it slid on the smooth garage floor and my car ended up like this:

http://www.nischan.com/crap/oops.jpg

lol

[Strahan]

PS, this is how it's wired:

Relay 1 (trigger relay):
85 - Horn trigger (two wires at horn, one grounds with horn button - this is the one)
86 - +12vdc
87 - To relay 2 #30
30 - Ground

Relay 2 (horn toggler relay):
85 - Momentary switch ground input
86 - +12vdc
87 - Stock horn terminal (the one unplugged for relay 1 #85)
87a - Air horn negative terminal
30 - To relay 1 #87

Air horn positive terminal junctions with relay 1 #86 and relay 2 #86 then to a 15a fuse then to the battery. I'm guessing on the amperage, not sure what is the proper amperage for air horns. Relay 2 #85 goes to terminal one of the dead pedal momentary then the other terminal on the momentary is connected to a grounded screw under the dash.

[MessyHonda]

looks loud....thumbs up dude

[Oldblueaccord]

looks good. use dielectric grease on everything esp the stuff down low keep the road salt at bay.


I have those ramps and I hate ramps cuz there always something jenky going on like that with them.


wp