a lot of reasons but some good places to start would be to check the fuse if that is good then the second place to look would be in the steering wheel which could prove really difficult being as there is an air bag there the problem could be that it isn't making connection to close the circuit and activate the horn and last but not least it could be the horn module itself which is located under the hood. (see where is my horn module located)
horn location for 2004 ford explorer
where is the horn located on a 1999 ford explorer?
horn not working on 2003 ford explorer sport trac, just a clicking sound
a blown fuse.
I believe the horn is mounted to the Explorer below the battery tray
Horn not working
I believe the horn is mounted below the battery tray
I believe the horn is mounted below the battery tray
I believe it is mounted underneath the battery tray
The 2006 four Explorer factory horn is located on the right hand side of the radiator. The horn will be behind the front grill.
Replace the horn relay. It is defective. Another possibility is a defective horn switch, but highly unlikely.
Short in the wiring, horn switch defective, or horn relay going bad.