Air horn wiring question

[satchel]

PLEASE READ ENTIRE THREAD, I ENDED UP WIRING DIFFERENTLY THAN DESCRIBED IN THIS POST----

I have installed some air horns and followed these instructions by travisgarrison:
- On the bottom of the fuse box there is a protrusion that slides out and reveals the wiring going into the fuse box.
- Find the small Orange wire (about 22 gauge) and and use a quick-connect to tap that orange wire with the negative wire from your compressor.
- Slide the plastic wiring cover back into place and remount your fuse box
- Now, using an inline 30A fuse, you need to hook the positive to the battery positive.
- I did this by connecting the fuse to the positive (using a quick-connect)
- You'll notice on the fuse box that there is a wire that runs from the positive side of the battery terminal to the fuse box. Unscrew the 8mm/phillips bolt about half way. Then slip the other side of the fuse wire between the bolt and the plate, and retighten the bolt. The advantage of this is that you can then hide the fuse and wiring inside the fuse box.

I did as he suggested and used the T1 screw in the fuse box for my positive. I am having second thoughts about his not using a relay as is supplied with my horn. I have a wire soldered to the orange 22 ga horn line. His connection to the 22ga wire from the steering wheel horn switch just doesn't seem right. Doesn't that mean that small wire is taking all the compressor circuit current clear back to the steering wheel ground? I think the 22ga is only meant to trigger the horn relay, which closes completing the circuit. The way I see it I should run the orange to my relay, connect the positive through the relay and provide a solid ground to the negative of the horn air compressor.

Was a tight fit here but worked. Didn't want to drill the cross bar so bent this strapping to hold the horns. Only hole drilled was in the corner of the battery box to hold the compressor.

[JimIsbell]

I dont know what he intended as I have only read what you posted here. But, yes, the power from the horn button should just power the horn relay and the relay contacts power the compressor.

[satchel]

Took that from his writeup here: Write-ups for my mods

Won't take much to add in the relay. I got the harbor freight horns that I think you suggested Jim. Off to the auto parts store for a fuse and a couple of push on connectors.
Thanks

edit: Well, it did take a little doing. Also had to tie into the + to the existing horn which is the blu/red wire on the same connector as the orange horn button wire on bottom side of fuse box. Used G2 to ground the compressor. Tucked relay, fuse and all under the fuse cover. No more road runner 'meep meep'!!

[satchel]

Word to the wise: There are two BLU/RED wires on the A connector under the fuse box under the hood. I was going for the existing horn wire(BLU/RED) and inadvertently connected to the head light(also BLU/RED). Glad it was still twilight out and only going five blocks this evening! Horn blared when I turned on the headlights so made it with the running lights.

[JimIsbell]

Thats funny, but you should have tested it before you left home. I am laughing so hard I will have to stop typing.....

[satchel]

Originally Posted by JimIsbell

but you should have tested it before you left home.

To be fair, it worked fine in tandem with the original horn when I pressed the horn button on the steering wheel(as intended). Was just a bit of a shock and then puzzle till I got back and got out the electrical manual. Glad it wasn't dark thirty yet. Glad you enjoyed some endorphins.
Off to fix it, hope there's not three blu/reds...starts raining, wipers go on and hooooooonnnnnnnkkkkk.......

[JimIsbell]

Maybe you could hook it to the brake light line, then when some SOB stops dead ahead you wont have to fumble for the horn while hitting the brake

[satchel]

I will never understand auto electrics. This still isn't working correctly. I have the relay terminal 30/51 connected to 30A fused circuit. Terminal 87 to the positive on compressor. Negative on compressor to body ground. Terminal 85 to the orange wire on connector A under the under hood fuse box, which is the wire from the steering wheel horn switch. I have terminal 86 connected to the blu/red which is the existing horn positive from the under hood fuse connector A. When I put a test light on this wire it lights up when I press the horn switch on the steering wheel, off when not, yet as soon as I connect to the 86 terminal on the relay the air horns blare. In other words the orange and blu/red trigger the relay WITHOUT pressing the horn switch on steering wheel. I DO NOT understand why this is happening, I've followed the instructions..............

After further investigation I found the orange wire to be hot at 12.8V???
Isn't this supposed to be usually open and grounded when the horn switch is pressed?? I placed a wire to ground instead of connected to this orange wire and it all works as expected now. Come to think of it, why did it work with the horn switch when I had it wired to the headlight? Jim, when you quit rolling around on the floor maybe you could explain.

[JimIsbell]

OK, I didnt relly follow your terminal numbers so I will just try to explain what you want to have.

The relay has two terminals that are on either end of the relay coil. Usually there is a picture of this on the outside of the relay cover. One end of this...doesnt matter which end....is connected to ground...frame of the car. The other end of that coil goes to the wire from the horn button that goes to 12V when the horn button is pressed and goes to "OPEN" i.e. no connection to ANYTHING when the horn button is not pushed. If there is no picture showing these two contacts then you can use an ohm meter to measure the resistance between the various (probably four) contacts on the reley box. There will be two contacts that should have a resistance between them, NOT ZERO. These two are the coil. If the relay is a double throw relay, which some are, there will be 5 contacts. In this case two of the three that are NOT the coil will show a dead short, ZERO OHMS. These are the Normally Closed (NC) terminal and the COMMON terminal. The third contact of those three is the Normaly Open (NO) contact. You can discerne the COMMON from the pair by putting the Ohm Meter on the NO terminal and on one of the pair that showed a dead short. Then activate the relay (put 12 V across the coil) and if you get a dead short than you have found the COMMON terminal. If nothing happens when you activate the relay then you have found the NC terminal and the other is the COMMON.

Now that you have identified the contacts on the relay, connect the coil as described above. And then connect the NO terminal to the horn and connect the COMMON to a 12V source to the battery. Actually, again, it doesnt mater which is which just as long as the contacts are in series with the power source. Now connect the other wire from the horn to the chassis, ground, car frame.

Now pressing the horn button will activate the relay by applying 12V across the coil. This will close the terminals NO to COMMON which will apply 12V to the horn, through the horn to ground.

Just think of the relay as a switch that is operated by applying 12V to it or not.

[satchel]

I understand how the relay works(and thanks for the detailed description of determining what relay contact is what), my question is why the orange horn switch wire(from steering wheel to relay in under hood fuse box) is always hot? And with it hot why did connecting the blu/red positive to extisting horn trigger the coil in new relay when it should(?) have been open(?) and not hot till the stock horn is blown(which I confirmed with test light)(and not grounded in either case?).
85 and 86 must be the coil in relay, 86 to go to pos+ on existing horn and 85 to push button horn switch according to diagram(this being why I tried to connect 85 to the steering wheel horn switch for ground, and ended up with 12V). 30/51 is the common and 87 the NO.
To reiterate, why is the orange wire(from steering wheel switch) hot and why does the pos+ to the horn trigger the coil when it(the untriggered pos+) should(?) be open?