same problem with mine. went to the lake, vts worked, played around, vts quit working. 2 hours narrowing down the problem, determined it was the relays behind the (MAGIC) VTS black box`but before i could get it off it started working again. assuming there is water getting in somehow.....
a good way to tell is to use a circuit safe test light that will tell you hot or ground. my xp is a few years newer but hot is constant and ground is intrduced via relay. one of my relays was stuck or shorted by water