Thanks mbdoc, I know that I have a massive compressor leak, but when I pass the sniffer along the large diameter hoses they still make the sniffer chirp, with increased frequency, especially along the protective plasic sheath on the suction hose. The hoses appear to be be in good shape, and the smaller high pressure hoses do not make the sniffer squeak at all. Exterior contamination maybe, oil or fuel? Compressor will be rebuilt or new, dryer and expansion valve also new, just thought since I was that far into it, might as well do the hoses too.