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but they have a dual battery set up? and you jump one battery to the other and it starts, that sounds like you have a bad connection between the batteries and the one doing all the work is going bad.


This was my thinking too. The batteries are connected in parallel, so "jumping" them shouldn't do anything unless there is a bad connection.

To the OP: The 80A fuse is your main charging circuit. If that's blown, your alt isn't recharging the batteries.

1991 Mitsubishi Pajero XP TD LWB family hauler.