Brevard county Fl, Tenants neighbor caused the AC to fail by shorting out the wires while weed eating around it, (I'm sure they'll say without consent), I (landlord) immediately repaired the unit once the tenants notified me that it wasn't working, (it took 3 days to get parts). When presented with the repair bill, the tenants refuse to pay.
. Who should pay the repair bill?

Sue whoever caused the damage and whoever ordered the weed work done.

Even if this was total accident , prevent it in the future by laying down plastic and bricks on the grass between the unit out doors and the house to kill off any grass that can grow near the connections so that this way there is no reason to run a weed eater near it again.