My never ending battle with horns

The 12 v positive is always there. The horn button simply supplies ground signal to close the relay. The horns must be chassis grounded. Moving them to painted sheet metal may have interupted that ground path. If you know that ground is good,
You can take the 12 V from the relay directly to the horn or supply the ground signal to the relay. Bang on the horn body with a screwdriver handle or similar. Wake up the neighborhood by exercising the crap out of those horns. Yeah they stick. Like the old saying "If you don't use it you'll loose it". LOL
Hope this helps.