holywood3645 wrote:Sorry but you are mistaken Bud. If there is voltage (12 volt you say) at the other side of isolation switch, the fuse would blow the fuse. Dead short. How would the 12v get there?
Current above 1amp to operate for any device, will blow the fuse.
James
partial quote
Not to beat a dead horse, and my last thoughts on the subject... Edit: I guess they weren't my last thoughts...
How would the 12v get there? Through the very devices you are trying to keep live by using that 1A fuse. The voltage potential passes through these devices even with no current flow. If the 12V wasn't present on that terminal the fuse wouldn't provide a path for the keep alive current to flow.
As your next line states, any current up to 1A will pass and anything drawing more than 1A will blow the fuse. ...and when the fuse blows, the 12V will again be available to the non-grounded terminal.
If you have a cutoff switch, turn it off and check for 12V on the non-grounded side of the switch using a meter (the meter completes the current path and allows the 12V potential to flow to ground). If there is no voltage present, you won't need the fuse because nothing is drawing any power from the circuit. If your radio, or whatever, needs a voltage to stay alive, there will be 12V on that side of the switch. That's a handy check for those "mysterious current drains" as well. Disconnect your negative battery lead and put a volt meter between the neg battery terminal and a good ground point. If you read any voltage at all you've got a leak.
Honest...