My 73 2.0 has dual horns and one of them doesn't work. Before I replace it does anybody know if they have different tones? Anything else I should know?

They do, look on the back they should be embossed either 350 or 400 hz

I've read on here they are repairable.
Don't remember who's thread but l hope someone knows the link and will post it.

I've tsken these apart on early 911's and got them to work. If I recall correctly, there's a screw in there that adjusts the frequency.

Test the seemingly dead one, by itself, with a 12V supply. When they both work, it's pretty loud.

Ive repaired a bunch of them, it can be fairly simple or extremely frustrating.

You mean Hz as mHz is way WAY above human hearing which for most people ends about 20 kHz.

--- bill

We just went through a horn that didn't work. There's contact points inside the horn that get corroded. There are magnet coils in there too that could get corroded, which could make it useless.