I had two 15" WOT coils, on two different machines (E-trac and Excalibur), fail on the same day! The E-trac version was working perfectly the day before, but, on the next hunt, wouldn't detect a coin laying on top of the ground. It would sound off if I waved my scoop over it, but not a peep with a coin. WTF? The Excal WOT, from the moment I fired up the machine, would give a constant, rhythmic, pulsating sound, even with the coil held up in the air. It would still hit on a target, but, it was hard to tell a target from a random pulse. I retested both today by changing to a different coil, and both machines are working fine, so, it's definitely the coils that are the problem. Can they be fixed or do I have to bite the bullet and get new ones. Neither are within warranty, at least I don't think so. I believe they're both at least 2 years old. Still, they should last longer than that, shouldn't they?