Travis Jordan wrote:
His Tek-Mate's sensor was probably bad.

The most common places for leaks in a system are the service valves at
the condenser (make sure the caps with o-rings are installed over the
schrader valves), the lineset (specifically, any brazed joints including
90 degree couplings, if such were used), then the evaporator coil. I'd
really be surprised if there was a leak in the lineset inside a wall,
although this sometimes happens when nails are hammered through
wallboard into the lineset.

Hung any new pictures recently?