97 V6
I am reporting my previous, frustrating horn issue.

Here is the horn wiring diagram. I cannot attach file. Here is the link.
http://www.justanswer.com/ford/7cyyg...recurring.html
The small diagram needs to be clicked for enlargement.

Problem: Horn stopped working

Diagnosis step 1: Found horn fuse blown. Replaced the fuse and pused horn button. No sound. Two possibilities, bad horn or bad horn wire.
Diagnosis step 2: Removed both horns and connected one of them to battery. Loud sound. Horn was not the issue. Blamed the wiring.
Diagnosis step 3: Measured horn wire voltage. 12V. Wiring was not the issue. Back to blaming horn.
Diagnosis step 4: Installed one of the horns and pushed horn button. Loud sound.
Diagnosis step 5: Installed both horns. No sound.
Diagnosis step 6: Repeated above steps.

What happened was only one of the horns was bad. It failed not because coil became open but because the plunger was stuck. So huge current went through the coil, depriving current from the good horn. Therefore, no sound, eventually blowing the fuse. When I tested the bad horn directly connected to battery, test wires got hot.

Had I tested the bad horn first or tested both, I could have solved horn issue on day 1.