I've searched quite a few OAT issues, but never have I found this one.
If the AC is off, all is well. The OAT registers properly. The minute I turn the AC on, it starts climbing about 2*F a minute !, even at highway speeds. This is the OAT, NOT the coolant temp !
If I turn the AC off, it will fall (slower)..
I've never had the AC on in this car and was preparing for summer.
Any ideas about what could be causing this ?