Richard
The GPS V and others have a unique but similar feature. They have two boards inside that are not hard wired together. In the 60CS there were three points that were spring loaded (like in some of the hand helds (VHF/UHF). Two points are the +/- for the batteries. The other I found was a backup battery that was hard soldered on one side and the other side was pushed onto the other board when the case was closed. I think that it was popping away from the board and not keeping continuity, so I put a piece of wire insulation tubing (like you use to cover wire joins, the heat shrink stuff or the firmer stuff) between the other board and the battery forcing it firmly onto the second board. And then scored the two copper points on board 2 that the copper/brass joints pushed against for the battery terminals. And bent the flaps more so they had more pressure against the board. And then back together and onto S40 and no problems. I have read where a service center does hard wiring for the GPS V for this same problem. You might try looking inside and see if you have a similar  setup. I know some of the older handi-talkies were like that, and if you were running or on a bike or M/C they would lose power. And it was that the man'f had not hard wired one side to the other. Most now have ribbon cables that come lose and cause problems (planned obsolescence so you buy a new one).
Stay warm on Bahstun. We hit 72 again today and expect 80 tomorrow. My ham buddy in Maine sent an email after his generator came on after the ice and snow got his power lines.
Bill
WB5ZAM
In the wilds of West Texas
2005 S40 (LS650-K5, or so they say that is what the new designator is).

where did you tap into to get power for the gps, i just added a garmin etrex legend to my savage and i want to hardwire it but i dont know how to go about doing it?