This problem could manifest as the dishwasher running nonstop and not entering the drying cycle. Academy Fellow john63 points us in the right direction:

Check the continuity of the HEATING ELEMENT with a test meter---if "open" replace the HEATING ELEMENT.

If "good"---it's very likely that the HEATER RELAY---located on the right side of the dishwasher at floor level---has failed.

During the DRY CYCLE---there should be 120 volts AC coming from the HEATER RELAY---to the element.

Most HEATING ELEMENT or HEATER RELAY failures occurred in homes that had a "Tankless/Instant Water Heater".

Other possibles are:

1) One of the DOOR SWITCHES FAILED

2) MAIN BOARD (very rare)

Part links:

Heating element ==> http://www.repaircli...Number=DMR78AHS

Heater relay ==> http://www.repaircli...1000260/2028620

Door latch ==> http://www.repaircli...400002B/1603323

Main circuit board ==> http://www.repaircli...Number=DMR78AHS

Source: Samsung DMR78AHS dishwasher runs nonstop and do not enters drying cycle