DuoTherm Heat Pump Icing Up

Well I finally got a solid reading on the Ambient Sensor, and it was way off and in the wrong direction. The chart provided by Duo Therm to check it starts at 55 degrees and goes up. I don't know why they don't give figures for 40 degrees and lower since that's where the defrost cycle is supposed to cut in. Anyway at 55 degrees there's supposed to be a reading of 11,667 ohms and it goes down significantly from there. At 65 degrees it's 8959 and at 75 it's 6939. Well it was around 45 outside and I got a reading of 7180. I think I'm going up on the roof and take the shroud off, find the sensor end and put it in ice water, 32 degrees. Then I'll see what it says. I watched the CCC thermostat and while it was in the 30s outside the thermostat never read "defrost" as its supposed to. I may have a bad sensor, but it also could be hooked up to the wrong place and getting abnormally warm temp readings.