lostmy battery amps -then battery fried then 2nd battery then starter went out-replaced batteries-,starter and alternator- now only 10 minuest later battery is low amping again! told the heater block was constantly running thou not on -almost on fir

deisel w/2 bateries yes.. my son in laws truck! traveling upstate lost battery amps. batteries went the starter went they replaced bothe bats starter and alternator! sat over night started today looked fine for a few min the n low amps again from ogden to layton he said a friend told him the heaterbox was continuosly running even when not on- dont knoiw why but he told me they almost got on fire sounds like short to me too but they said all checked out fine..dont make sence here either to me but obviously a problem..just dont know what to do to helpo them we are all un educated on vehicals for the most part but basic reasoning i do have..i suspect wiring harness some how ? any more advice?

If it not pretty obvious when looking around under hood at the positive battery cable and alternator wiring then it is most likely beyond DIY repair.. Suggest having qualified personnel check it out hands-on.. There's just isn't any protocol for this type of problem, no cut and dried Internet solution .. In fact it's very few times there actually is! .. Good luck with it!