Our MH has roof horns that are old and weak. Also two "snail" horns under the hood. No electric compressors that I can find. It is possible to dismount the air horns and clean insides. Don't wan...
I have used Stebel Horns in both my motorcycle and auto. Sound is at 140 dB. Really gets people's attention. It has its own little air compressor and runs off 12VDC.