2015 GMC Terrain wipers, windshield & visibility problems

If we use any climate control setting before using the defroster, then try to use the defroster, it will only blow cool air. If we change the setting to vent, heat or A/C, warm air will blow, but switch it back to defrost and only cool air blows from it. We could not clear the windshield of fog in a warm rain without turning the defroster all the way to hot (95 degrees). As this was in the middle of summer, it was unbearably hot in the car trying to drive.

I was driving down the highway doing about 65 when I ran into a bad thunderstorm when the windshield wiper suddenly stop working they was on high speed, which was very dangerous because it was the driver side wiper. I had to pull off the highway until the rain stop!