You can check to see if the clutch is bad by taking the tension off the drive belt then grab the clutch and check for play. Mine had a lot. to change the clutch the pump has to come off so you loose the charge but it's not a bad job.

 

Thought I'd post an update on my situation as it sounds similar to OP's issue.

Made that same horn type sound yesterday for the first time ever. Very loud. Had been blowing ice cold without issue prior. Diagnosed today, needs a new compressor, clutch, serpentine belt and have the system evacuated, etc.

Bill is $1089.00 and I'll have the truck back tomorrow.

Went with an aftermarket (not remain) compressor. Mainly because it has a lifetime warranty and the motorcraft part did not. Also, I had issues after issue with ac components when the truck was still under warranty.

Left it at the shop over night as they said driving it would possibly take out the serpentine belt.