When you say coolant temperature, do you mean the the pre-installed CHTs (which are in the heads, which makes them coolant temperature, effectively) or do you mean that you've added a separate coolant temperature sensor?
Currently, the only officially-supported coolant temperature sensors are the Dynon ones: 5/8-18 UNF (Dynon P/N 100409-001) and 1/8-27 NPT (Dynon P/N 100409-000), and also Rotax p/n 801-10-1 (this is the same as the pre-installed Rotax CHT/Oil temperature sensor. Unless Do you have the 1K resistor installed as documented? Which sensor type are you using?