The horns in my 745 stopped working reliably, with a thin "bleet" instead of a round tone. After inspecting, I found both to be completely rotted out with rust. I bought two new horns from FCPGroton (Volvo OEM horns were less expensive than the Bosch replacements, BTW). One bolt holds each horn: a little PBlaster and it came right out. The connectors were stuck in place and had to be pried out using a narrow screwdriver in the slot on the horn connector holder. I sprayed each connector with DeOxIt to remove the heavy oxidation, then filled the wiring connector with silicone dielectric grease. I popped the connectors back on and voila! great sounding horns. Total investment: $110 for two horns; about half an hour lying next to the car. Hot tip: the horns are the two-connector variety; most aftermarket horns are single connector. The latter requires an additional relay, so better to buy Bosch or Volvo drop-in replacements.