Bro,no point u asking here and straight away go change the parts to new one as we are jus giving u some idea.

First of all i suspect it's ur wiring.U can check ur wiring at some battery shop where they do provide wiring check-up.Don't waste ur money by replacing this and that just because u/shop guy suspect it could be the culprit.Makesure which part is the culprit and only replace that particular part.