Microwave question

[Masquernom]

Our over the range Microwave died, and I just replaced it with a new model from GE. We have a gas range and oven below the microwave. With the oven on and some burners while my wife was cooking dinner, the vent fan on the new microwave turned on at high speed to keep it's electronics cool. It's very loud. It can't be turned off or, like our previous unit, set to slow speed. DW says it has to go. Apparently it starts the vent fan at 150 degrees F.

Does anyone else have a newer, over the range unit, that starts the fan automatically at low speed? Owner's manuals I've read online are not clear on this subject for competing brands.