A/C Clutch Power !?!?

My 2001 1.8T A/C went out & I found it is getting no power to the compressor clutch. After seeing this in some previous VW's I replaced the fan control module because all fuses, connections & freon level were good. The signal I'm getting at the compresor is a split second voltage signal & then it's gone. The clutch does not engage and I see the same signal with or without the harness plugged in at the compressor. No fault codes in this car and everything seems to be in good order. I can't figure out why my A/C just quit and shows no visual problems that I can see. Is it common for the controlhead in the dash to fail? Both my lights are working on the A/C & Recirc buttons -- I just wish I knew what to check next or could find a troubleshooting sequence that showed some voltage & sensor values or Fan Module inputs etc... ----HELP----

There must be a lo/hi pressure switch somewhere in the refrigerant circuit which may be open (you say freon/R134 is OK but switch may be buggered). How are the fuses on top of the battery box?....they must be 100%

FYI Guys -- Thanks for the response but this circut was sending a signal to the clutch coil & then the signal would go way because the clutch coil was open & the circut was not being completed. Replacing the compressor & clutch has fixed this car.
Thanks to this Forum for help with problems