I suspect you DO have an Ambient Air Temp sensor. My understanding is BMW uses inputs for ambient air temp in controlling the A/C and electric condenser fan. It should be located on the drivers side front, clipped into the bumper cover. You can search for what it looks like on ebay. realoem.com, or getBMWparts and then poke around looking for it on your car. However, how you would get it to display, I don't know.