Thermo King C600 not cooling

ETV good, TXV just replaced, compressor good, Freon good.
I got C600 unit, its not cooling, when start the unit ETV start raise until around 180, temperature difference around 6F-7F. But when the motor start run at high speed ETV start drop and stay around 20-30. temperature difference only 2F.

Currently known issues: Water temp sensor get random numbers, jump from 100 to 250 or no reading. (The dealer said they used wires to connect the motherboard directly to the sensor and get same result, even with new sensor)

Now they think there is something wrong with the motherboard and needs to be replaced, the unit does not have any error codes, is there any other possible way may cause this problm?
I know ETV can work reverse, maybe a god knows reason the ETV got short circuited and start work reversely?