At first I cycled the power to the unit by flipping the breaker. The unit would start working again but then a few days later it stopped cooling. Then a day later it stopped cooling again. A friend of mine who just retired from repairing appliances said that it was probably the PBA main board. I replaced the board six days ago and so far, the problem has not reoccurred. The repair was easy. Unplug the unit. Just two screws, remove the cover and unplug all the connections, pull the board and install the new board, then re-plug all the connections.