12 Volt Airhorn Amperage

I'm fitting a airhorn into a car but It does not show me its amp strengh or wattage in order to calculate.my multimeter is rated for 10A, I'm just afraid I might damage it .its the normal red air compressor with the 2 horns and see through pipe.I'm going to use the existing factory wires for switching of the relay.

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.

I assumed 30A for mine, probably because that was the rating of the relay it came with.

Why do you want to know? Else just assume 30A. As long as the fuse protects the wiring things should be safe even if you have , to upgrade the circuit to prevent fuses blowing.

So 10gauge should work fine with a 30A fuse?

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.

Also advise if its needed for a relay,can't I use the existing wiring as it already has a factory relay?

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.

If your relay and its wining and fuse handle it, you can use it. That probably means it replacing your existing horn(s) which afaik are usual ~5-8A each.

However a with all high current additions, I usually advise separate circuits.
Ad in my case, airhorns have always been fitted with a selector switch so I can use just the OEM or plain horns and only switch in the airs for country driving or real bad situations (where they usually also trigger headlights).


As to 10G, according to powerstream's American Wire Gauge table it's fine as chassis wiring (55A) whereas for power transmission (unbundled air mounting) it's only 15A though that should be ok given the short term nature of horn use.
I look upon 10G as being a 150mV drop per meter at 30A which IMO is ok for a horn assuming a typical (front) battery to (front) horn short run (via a relay).

Note that others here generally use other wire gauge tables, and I only use them for the raw data so I can calculate voltage drops (which is how I size my wiring) or see how they current-rate their wires (ie, my sizing should never be less than what tables state).

15-20 is normally OK, or feed in parallel from your existing horns and up the fuse to 20 amps.
BTW The brand shown, the tubing is bloody awful, hot water or WD-40 to erase them on.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Thanks a lot Howie!think ill use the existing wires.looks like 12gauge.

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.

Hi Howie/Old Spark! I have fitted the horn succesfully.I used the existing wires for switching on the relay and the horn works 100%.I have one problem,the factory keyless entry beep does not work anymore. As far as I can imagine it is still suppose to work via relay with the new horn.do you think it reseted when I removed the battery terminals? Its a Toyota corrola 2004 sedan.your feedback will be highly appreciated.

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.

Shouldn't have made any difference.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

It is a factory +tve switching circuit.ill ask the guy to check the manual out as the only wire I removed was the one wire from original horn and used it for +tve switching on the relay.thanks.

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.

Read my previous post where I told you to wire the compressor directly to the OEM horn wires, don't use the supplied relay and increase the horn fuse to 20 amps.
That's how I do it on Toyotas.
Alternatively, find the NEG horn push wire either at the steering column or where it joins the horn relay (assume engine bay) and trigger the aftermarket that way.
There are actually three ways to wire this and none should affect the alarm beep unless you CUT the leads to the OEM relay or blew a fuse. Check your fuses.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Thank you howie! I will check the fuses,think it should be a fuse as the indicators are also nolonger flasing when using keyless entry.I have not cut any wires except transfering them to the relay.ill try and hook it up straight to OEM wires tomorrow and use a 20A fuse.

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.

You'll probably find the airhorn is too slow for the beeps.
And IMO so it should be - it's bad enough with horns beeping for central locking and alarms - I usually feel like rocking such installations if not the people using them. But to have an airhorn blast instead...

My air horns oscillate only when the alarm is triggered, not with on/off or warning chirps.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

So if the airhorn is too slow for the beebs,the horn will still not sound if I hook it up straight to OEM wires? Correct me if I'm wrong.the guy says it makes fff fff instead beep beep.if I hook the OEM horn up again on the OEM wires,and then still use the same wires to trigger the airhorn via realy just so the guy can hear his beeps?

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.

Are you asking? IMO your last question is a statement, else rhetorical.

Relay actuation delays should be negligible (typically under 10ms) whereas airhorn pumps take longer to spin up.

The airhorn will just be used when hitting the switch on the steering,then both will sound .when he use the keyless entry,only the factory horn will sound.I understand the airhorn will not sound with the keyless entry as it is too slow.

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.

Thank you for your patience and time.client just contacted me,told me that the horn does work when you trigger the alarm.its just that it doesn't work with the beeps.anyway he said that isn't that important aslong as it goes off when it gets tempered.thank you for your advice guys.don't worry everything sticks like glue what I'm learning from you.

-------------
Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.