I failed an inspection yesterday because my horn wasn't loud enough. The guy that worked at Jiffy Lube said there is a diaphragm I can adjust somewhere. Is this true, or anything else I can due other than buy a new horn? If nothing I'm gonna buy this: http://www.hornblasters.com/products...8-air-horn-kit

 

I have seen it on some horns. It is just an adjustment screw on the horn. Find the horn and check it for a screw that is not used to mount the horn or connect the wires. Make small adjustments until it gets louder.

If it has no screw, you are out of luck for adjustment. Go to the junkyard an pull one from another vehicle. I pulled one from a Ford Taurus for my 72 Chevelle. Be sure to test it out.