2000 SERRIA, HORN WILL NOT WORK WHEN YOU DEPRESS THE HORN BUTTON, WILL SOUND OFF WHEN YOU PUSH THE ALARM BOTTON, WHAT IS THE SOLUTION. JOE, POQUOSON VA.

Switch in steering wheel failure

Do you have an air bag light lit on the instrument cluster ? Do you have C.C. button's on the steering wheel , do they work ? If the alarm fob (as u call it ) Can make the horns sound , the relay is sending B+ voltage to the horns Don't know how your testing.
System Description
The horn system consists of the following components:
• Horn fuse
• Horn relay
• Horn switch
• Horn(s)
• Body Control Module (BCM)
System Operation
The vehicle horns are activated under the following conditions:
• The horn switch is depressed.
• The body control module (BCM) commands the horns on. The BCM commands the horns on under either of the following conditions:
- When the content theft deterrent system detects a vehicle intrusion. For further information, refer to Content Theft Deterrent (CTD) Description and Operation in Theft Deterrent.
- When the panic button is depressed on the remote control door lock transmitter. For further information, refer to Keyless Entry System Description and Operation in Keyless Entry.
- When the OnStar® system is used to sound the horns, if equipped. For further information, refer to OnStar Description and Operation in Cellular Communications.
- When the keyless entry system is used to lock the vehicle, a horn chirp may sound to notify the driver that the vehicle has been locked. The notification feature may be enabled or disabled through personalization. For further information, refer to Keyless Entry System Description and Operation in Keyless Entry.

Circuit Operation
Battery positive voltage is applied at all times to the horn relay coil and the horn relay switch. Pressing the horn switch applies ground to the horn relay control circuit. The body control module BCM may also apply ground to the horn relay control circuit as described above. When the horn relay control circuit is grounded, the horn relay is energized and battery positive voltage is applied to the horn(s) through the horn control circuit. The horn(s) sound as long as ground is applied to the horn relay control circuit.

The actual alarm horn may be disconnected /shorted bad ground or burnt out . Is the alarm horn the same as the car horn? Does the car horn work? Alarm horns popular for burning out.

check the battery in key, check wiring harness to relays behind dash. I think you have a bad relay or connection or button on your key is sticking. Worst case is having shop diagnose system so you can repair.

Just hold the lock and unlock button on your key until you hear the horn again. Then its activated :)

when you depress the horn, the relay should click, if not then the horn button or connection is bad. these have 2 buttons, right? it doubt both could be bad. if just one big horn pad, pad could be bad

Have you tried resetting the alarm, or even disconnecting the car battery and reconnecting it... also make sure all doors and trunk lid is closed

If the air bag light is on, the horn does not sound when the pad is depressed (but does souns when you activate the alarm) and the cruise control doesn't work (but the lamp lights up when you first turn the key on), your issue is probably with the clockspring. This is a device that keeps an electrical connection between the steering wheel and the rest of the car regardless of steering wheel position.

The horn button itself is the switch therse power to the horn button and you push the button to complete the cicuit to the horn.if the horn is bolted to the body it is already earthed and requires power to work not earth.

The horn(s) burn out very easily, also there is a relay, press the horn button repeatedly and listen for a click noise (it may be under hood), if you don't hear it the relay may be at fault, if you do the horn is burned out, not uncommon.