73 delta 88 conv. 350 v8 4bbl h series
 

looking for info re: firewall relay. when i hit the horn it does not sound but the relay (center firewall, top) clicks. there are no numbers on the relay but it is a delco remy. when the alarm was installed the installer ran the power to the alarm horn to it. alarm horn works and i replaced the car horn. can't figure this out. if the alarm horn works why wouldn't a new horn work? what is this relay?