It sounds like the security alarm is stuck. While this is happening take the key out of the ignition and shut the drivers door, then lock and unlock it with the key. If the problem stops even for a minute then the alarm is the problem.
the horns are behind the fog lights underneith the car, one on each side of the car
1999 mercury sable horn replacement
Poor ground, or defective horn.
The horn is locared on the LH front of the vehicle, below left headlamp
For a 99 it is behind the right rear quarter trim panel.
Horns normally use a breaker, not a fuse.
You can disarm your 1997 Mercury Cougar alarm system by removing the alarm system fuse. The alarm system fuse can be found in the fuse box.
I believe it is mounted below the battery tray in the engine compartment
below the fog lights there is one on each side
Under the battery tray. A little difficult to get to bu tnot too bad.
It's under the hood on the passenger side in a black box behind the battery.
I have changed horn modules on a 1994 Cougar, which should be the same from 1993 through 1997. There were two horns (one low-pitch, one high-pitch) located in the engine compartment located near the bottom of the radiator, one on the left and one on the right, about 24 inches apart. The Ford service manual I located the parts in indicated that for my 1994, the dual-horn configuration was normal.