I don't think the sensor would be near the fan. The unit gets quite warm inside when it is running and that is what the fan is for.
Ideally, the temp sensor would be in the neg clamp so it goes on the neg batt post. But then, the instructions say to put the neg clamp on the frame when the batt is neg frame grounded (to prevent sparks) so that wouldn't help.
I still recommend leaving the batt and the charger at 72ish for several hours and then see what it does for your baseline, then decide if it is working right or not.
