Most horns are that type if you look deep enough. Simply breaking the vibration setscrew loose can often get them working again, or cleaning up breaker point contacts to make them low resistance again. Water entry or rust usually the problem. I haven't bought a horn in 40 years, I always can fix them. I, like sailor learned long ago from motorcycle horns. Only reason to buy one is for when they cheap out and give you only one and adding the opposite tone then really ramps up the noise.
I wouldn't be spraying WD40 in there, once it hits current, the current will convert it to something (bubblegum) that does not help passage of that current. It's not electrical cleaner.