I am try to up back up the transformer that goes on the ac unit in the house. I need help with what wire goes where.

If your transformar only has four wires which are Black, White, Blue and yellow. The black and white aare the high voltage wires and should be connected to the power. The blue and yellow are the low voltage wires.

If your transformer has more wires than theat you will need to tell me what they are.

The transformer has four post how do I know witch one goes where. It's a 4000-02c02ae52