Your alternator is capable of producing 70amps. If your van has sat a few weeks, the battery may be low and asking for more amperage to recharge. When you rev the engine the alternator is putting out more amperage than the fuse can handle. I believe the ampacity rating of 16 gauge is maybe 10amps. So, the big question before you try putting a 70amp fuse in that holder is, "What gauge is your charge wire?".