99 s70 glt Horn not sounding properly

[AVIP]

Was looking at a family members s70 when they came to town today. They were first worried by how the horn doesn't sound when the car is off. Which I assume is normal. Doesnt in my car either. But then I got stumped

Car was on and when I sound the horn sometimes it never plays. Sometimes it plays only one tone. And more commonly plays one tone and two seconds later the other so its the full horn.

What causes this behavior? Horns looked like they have been replaced and all the wiring looks good under the hood from what I can tell.