Well here is one for ya..oooh::wink: My GPS suddenly quit working:confused2: The screen said " GPS module not responding" figured it wasn't good. So here we go.. Step #1....Johnny has the exact same 520c as mine. He brought his unit & plugged it in still said "GPS not responding" so it aint the graph...whew... Step #2. We had to fish in my boat in a tourney last week plus went to Tawakoni for a gathering so we used his Lowrance 37 with internal antenna on my grapf hook ups everything worked fine!!! Step #3. One of our friends at the tourney had a lowrance 2000 gps antenna so we unplugged mine & put his on.....same response "GPS module not responding" double whew 219.00 for an antenna Step #4. Switched the "T" with his ....same response Step# 5 Think,Think, Think,oooh: has to be a wire... Step #6. Trace wires from unit to where they hook up..1st the hot wire there are 2 one for gps one for graph turned on unit disconnected one at a time both went off.... Step#7 did the same to the ground wire..unit went off.... Step#8. Has to be the cable from the unit to the GPS antenna...so i drilled out the rivets and removed the cover. The cover goes from my side console to the back of the boat along the rail and the deck it covers all wires, bilge hoses , shifting cables etc....1st thing i seen was the cable UNPLUGGED !!LOL It has a split before you get to the "T" that puts them together..Here is the deal it screws together at least 1/2 inch of threads...the dealer must have got side tracked at that point and had them plugged in but forgot to tighten it up!!!! Man that saved a lot of $$$$$$$$ So here is one for the record books!!!