horn went flat
 

I'm back again. This time my horn went flat. Someone cut me off and when I honked the tone of the horn was different, from low pitch to high and squeaky. Is this a horn replacement or maybe something got inside the horn? I found a resource to be able to do this myself. I found some oem parts but also these are cheaper:

https://www.pelicanparts.com/More_Info/99663520504.htm?pn=996-635-205-04-INT&gclid=EAIaIQobChMI_oOLvvai3QIVBdtkCh3RXgUBEAQY ASABEgLwnvD_BwE


Will either of these work on a 09 C30?

Also, usually do both need to be replaced or just one or the other? I know I could check but I wanted to open it up only once.

Ah, Volvo aren't what they used to be! Not much to a horn, really... Only one should be bad, just replace it, the Pelican deal seems OK.