1996 sts battery drain? on 1996 Cadillac Seville STS

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1996 sts installed new battery after i thought the one that was in there was bad - I put in a goo napa with 1000 cranking amps. car runs for a few weeks then sits a couple of days then dead.. voltage is showing good 13.5 to 14.0. when running & checked by my mechanic what do i do
(1) Answer
It needs to be checked for parasitic draw. If it goes dead only after a couple days. It should be easy to find. Unless, it is an intermitant draw, then it may prove a little more evasive to find. Pretty standard electronics testing skills, should be all thats is needed, to isolate the problem.