Question is not 100% clear.
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1) Are you trying to repair a transformer?
I do not know of any repair for the transformer, or available parts sold to repair transformer, although the product does have a warranty, and Intermatic might have a repair protocol for the transformer.http://www.intermatic.com/customer%20service.aspx
2) Are you replacing existing transformer with a new transformer?
The transformer plugs directly into outdoor outlet, and wires are connected to A and B terminals.
Open following link to read how to set up and use transformer in troubleshoot-format:http://waterheatertimer.org/Malibu-power-pack-stopped-working.html