I have dual horns on my Avanti and the Lo range one is not working. It is a riveted case and I am not sure it is repairable. Anyone have experience with fixing these?

It sounds like it wants to turn the armature but is badly gummed up. Would applying more volts (24V?) maybe break it loose? Can I spray switch contact cleaner down the bell mouth or would that just hit the diaghram? Any ideas are welocme but it looks like cracking the case would ruin it.

It is out of the car and I hooked it directly to a 12V battery to test it.