Horn works when you hit the alarm button but dont work when you hit the horn from the steering wheel

It appears to be a well documented issue!

https://www.google.com/search?q=2007+sahara+unlimited+horn+relay+location

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check the power from horn switch at steering wheel and also the harness going through the column

If the alarm horn is the same unit used as the car horn then your problem is the contacts for when the horn is pressed. Some horns are activated by pressing the large center area of the steering wheel others have little buttons on the left and right side of the steering wheel. If the latter is the case make sure you try both pressure buttons to see if horn will work. Either way the contacts have to be cleaned or the wheel needs to be adjusted to allow the contacts to touch each other when pressed. That's most likely your problem.

You have 2 point of contact one is the alarm and the other is the horn switch itself, the horn switch is non op,

if your horns work with alarm using remote, then fuse and relay good if you hear no horn using remote set off alarm,and horn pad dont work, replace horn fuse and relay, if both okay, you have to replace the whole horn pad with air bag in steering wheel both horn control pads and airbag is one assembly.

you may have a problem with the clock spring or spiral cable as nissan calles it. it is a part of the air bag system and also horn signal runs into and out of it.if that part is bad, your air bag light will flash and your horn will not work. has anyone been doing any repairs inside of the steering wheel?? it may just be unpluged. if you are going to tackle this your self to look inside of the steering wheel, make sure you disconnect the battery for at least 3 minutes, befor you start playing with the air bag. you dont want to blow it up.

alarm wire most be interupting with the horn wireiring.some most be wrong with the alarm intaletion,it like you having a short circuit.

If the alarm makes the horn work, then it is not the relay.
It is the horn contact or slip ring.
You need to take the cover off the steering wheel center.
But this could be dangerous due to air bags.
Disconnect battery first.
Steering wheel might have to come off.
Recommend a shop because most people don't have the tools for pulling steering wheel.

first check for power at horn.

If the horn works with the alarm button but not with the steering wheel horn pad the problem is most likely in the contacts beneath the steering wheel. This requires pulling the steering wheel and repairing the contacts.
If this vehicle has an air bag in the steering wheel make sure to deactivate the airbag circuit before pulling the steering wheel.