That;'s what I thought
The sensors are a temp dependant resistor - pot for sim - to ground between a voltage divider, with the Inlet Air temp is on A0 and the coolant temp is on A1. And it you don't pull up or down on the other when it's not connected to the pot they can affect each other. A0 IAT was fine, but pot on A1 would make both move together without the puller on A0.