Your going too deep, it's unlikely to be the loom itself!

You need to work systematically, i.e. look toward the said gauges first and then disconnect the instrument cluster etc.

Something else that has come to light as well (no pun intended) is that you say you have changed the dash, therefore you want to check you haven't trapped any wires in the process of fitting it!

As I said originally, it has nothing to do with charging!

Martin