its a side by side freezer/fridge

so both the fridge wasn’t cooling down and the freezer items started to defrost.

there was a lot of ice visible on the freezer inside panel. so i checked the following:
1) thermostat..it was closed (showed continuity) when it was frozen and it showed open (no continuity) when at room temperature. means = thermostat is good
2) checked heater wire: shows a resistance of 23.7 ohms…i think this is good, right?

then i removed the thermostat, and joined the wires together to bypass the thermostat to ensure the loop is closed, then:
3) voltage at the wires for the heater measure = 6.7volts
4) i had a spare defrost control board, put it in there and measured the voltage at the wires, replaced it and the voltage still measure 6.7 volts at the heater wire.

question:
1) what voltage should i be reading at the wires at the heater…120v AC, right?
2) by connecting the wires for the thermostat, i have closed the loop right? so the board should be sending voltage for the heater wire to turn on, right?
3) what is wrong?
4) how do i know if the defrost control board is bad? at the white and black terminals on the the defrost control board, it measures 120 volt

Edited by user Saturday, June 6, 2020 6:44:14 PM(UTC)  | Reason: Not specified