I've had my stebel horn for about a year and it started "squeaking" instead of "blaring" a couple of weeks ago. It's raining today so I finally took it off and started experimenting. Mine is mounted under the left side plate (1st photo). The fuse and power were good, the compressor was strong, and when I finally detached the plastic housing from the metal compressor, I could feel a powerful blast of air coming out of the port (last photo). I knew the problem had to be with the resonating chamber or plastic part. First I used an air hose and nozzle to make sure all the dust and dirt were removed from inside the plastic chamber. When I first put my air hose nozzle (2nd picture below) inside the port, all I got was the sound of wind going through. I tapped on the round metal resonating chambers and I started to get sound. Did some more cleaning and tapping and finally started getting the full blast of sound like when it was new. Apparently the chamber interiors had frozen up and weren't flexing any more. After reading some of the past threads about horn problems, I noticed that someone mentioned drilling a hole in the bottom of the plastic chamber to ensure that water drains out. I thought it sounded like a sensible idea. DON'T DO IT. As you can see in photo 3, I drilled two small drain holes in the bottom and the sound immediately changed from a blaring sound to a high pitched squeak. I had to use two small screws and some sealant to close them back up. Now it sounds like new again. I had to use some gasket sealant on the male port when I reinserted it into the compressor body (last photo). Just wanted to pass this along since it saved me about $60 or $70 for a new one. Oh, my camera is still screwed up so it's showing a lot of pink or white color in the photos that really isn't there.