txbayou,
I don't think your fan was running if your temps were higher than your 5 in 1. If you put a thermometer in the shade, vs in a shield under direct sun, it will read colder, and read too low. Most believe you should put the sensor under a tree, or under an eave. This is wrong.
It wouldnt be the first time that Im clueless, so heres where Im coming from: My acurite tower hanging near my front door matches the reading at a nearby big airport (where I think they probably have a competent measurement setup) very closely, even exactly, on the hottest afternoons. Ive been watching this all summer long. So I consider the temp reading from the tower good nuff to be my reference temp. for the afternoon, whether the location of it is proper or not.
Fans running or not, neither 5/1 nor Atlas was ever able to come close to the tower reading, as soon as the sensors were in full sun. Atlas was even higher, by several degrees, than the 5/1. With 91 on the tower the other day, it was briefly 101 on the Atlas. It was an immediate downer to see one more Acurite sensor that cant keep up with the heat, just this time at a higher price.
With the additional issues that the Atlas was having, it was for me a clear choice to return it.