If the problem began after he switched some batteries around, it may be he incorrectly hooked up the wiring, so check that first. If the wiring is as it should be, then there are two things to try:
- Re boot the touch pad by unplugging it for a few minutes. Go under the dash to access the plug at the back
- In every Cat that I have had, the terminal block is in the battery compartment screwed to the transom. Take off each connection, clean it, apply dielectric grease, and reconnect. Often one of the grounds on the block is the issue.