Second Horn

With any kind of air horn, this circuit will blow the factory 10A fuse as soon as you activate the horn button and the added switch is on. Well...maybe the 2nd time. How do I know this? I made the same mistake and I'm an Electrical Engineer! The air compressors for the air horns have a huge starting current, probably about 10-15A. I just followed the instruction that came with the air horn, which said the added relay was optional. Mine is wired with no added switch. Since I have only 1 horn, I used the unused 2nd horn connector to actual the coil of the added relay and then an 8A time delay fuse from terminal #30 to the battery.

Shouldn't the relay just trigger a release valve for air horns while another line straight from the battery runs the compressor? I'm thinking about an actual compressor with tank, pressure switch, etc.

Also, you could just use the factory horn wire to activate the relay (pin 85), and have pin 30 run fused to the battery. That would bypass the stock fuse.

I use the factory horn wire like Tiger suggested and ran a hot wire with a fuse link straight to the compressor.

a lot of the smaller air horns don't have a tank, just turn on and off the compressor, the whole unit is about the size of a beer can and then tubing to th horns themselves
so there is a pretty good current draw when first turned on !
forget where but another post about using a relay as they blew the fuese each time they hit the horn when just swapping plug from stock to small air horn
and remember ( at least back in the old glass fuse days)
if i have a 15 amp fuse and hit it with 12 amps several times you can see the filament dip and just a matter of time till fatigue and it blows

note: beer can size is considered a official carolina alliance measurement ;-D

I thought those other horns were designed to replace stock ones, and as such wouldn't blow fuses. Then again, I never did see wire diagrams for them so.... :dunno:

You wouldn't happen to be the same phantom on TW would you? Since you mention the carolina alliance and all....

ooops , my cover is blown ;-D

92pickmeup said:

With any kind of air horn, this circuit will blow the factory 10A fuse as soon as you activate the horn button and the added switch is on. Well...maybe the 2nd time. How do I know this? I made the same mistake and I'm an Electrical Engineer! The air compressors for the air horns have a huge starting current, probably about 10-15A. I just followed the instruction that came with the air horn, which said the added relay was optional. Mine is wired with no added switch. Since I have only 1 horn, I used the unused 2nd horn connector to actual the coil of the added relay and then an 8A time delay fuse from terminal #30 to the battery.

Click to expand...

What kind of air horns are you talking about?

When I press my stock horn button in the steering wheel it sends voltage to either the stock horns or to the air solenoid valve, which then opens up and lets the air flow to the horns. I have a spdt switch that controls whether the stock horns are Live or the air solenoid is Live. The solenoid pulls less current than the stock horns, so there's no relay needed. This circuit has nothing to do with the compressor motor.

The air compressor motor circuit consists of 8 gauge power wire from the battery, to relays, which are controlled by a pressure switch on the tank. The relays are also controlled by a switch in my cab. The switch has to be On, and the pressure switch on the tank has to sense low pressure, and then the relays will be engaged and the compressor will turn On, filling up the 5 gallon tank and the air line that runs up to the front of the truck where the air solenoid valve is.

Cut the 12v+ wire going out to the stock horns, connect it to #85 on the relay.

Pb- Were you up too late last night?

Pb said:

^ Instead of adding that extra relay why not just do this?

Click to expand...

' Cause the circuit above has your factory horns blowing constantly -well, until you blow the air horn. (Battery to 30A fuse, to pin 30 thru norm closed contact to pin 87a, thru 10A fuse thru horns to ground.)

msibille said:

' Cause the circuit above has your factory horns blowing constantly -well, until you blow the air horn. (Battery to 30A fuse, to pin 30 thru norm closed contact to pin 87a, thru 10A fuse thru horns to ground.)

Click to expand...

:lol: I was thinking the same thing. Then he mentions moving the horn wire from 87a to 85. That would work.

Yeah you're right. I overlooked that. I guess it would take two relays.

caribe_makaira said:

How about this? (like I said add others...)

Click to expand...

Yes, that will function without blowing the 10A fuse.

Pb said:

Oh, are you talking about this kind of horn?


That's childs play.

Click to expand...

Yes, that's one of them. It also comes with a relay. Mine is similar, but has dual horns that are separate instead of integrated. The "beer can" compressor is the same on all.