wiring issue

[mystur]

hello all,
recently picked up a 1980 gmc truck, having some issues from the p.o what he has seemed to have done is for whatever reason the dual tank selector switch has been wired up to a always  hot or constant 12 volt source which in turns kills the battery within overnight timeline.my question is can I or should I rewire this to a switched 12 volt source that only has power when the keys is on?. any help would be greatly appreciated

[bake74]

     First off welcome to the site, here is a wiring diagram for duel fuel tanks (provided by Backcountry).

     Also in the tech section is the manuals for all the years of our trucks including the service, unit repair, wiring, etc.  These will help you along with the wiring diagram picture.
     You should check your wiring and make sure it is not hooked up wrong or crossed/shorted somewhere.  Let us know if you need more help and we will be more than happy to help.