1040 solar displays a warning that says 100 degrees C while riding when its not warm to the touch and sat ambient outdoor temps in the 60's F

I have the same issue unfortunately 

That's a message that 100 calories have been burned. I got fooled too when I was new to the device. It will flash every time it calculates you have burned 100 calories.

That makes sense now.  Thank you - much appreciated 

Same issue here. That 'alert' could be a LOT more clear... Showing a flame icon gets us thinking that the unit is trying to tell us it's overheating. Quite puzzling as it *might* have been 100F on a hot day in the sun... but 100C would have been insane. That's why I'm here searching the forums, because if the unit is overheating in a Minnesota fall it's never going to survive the African desert ride I'm training for. But low and behold, it's just telling me I burned calories, lol. Garmin engineers, I hope you're watching these forums and update this alert to be more clear.