I have a 2019 Blazer RS, roughly 65,000 miles. Its been really cold for a few days so i start the car early to get the engine warm and turn on the defrost for the ice on the window. I went to the car temp was 205 ish defrost was blowing ice cold. thought maybe it needs some pressure so i hit the gas held it at 1500 rpm for about a minute and still cold. so i cleared the window myself and drove drove it. hot air came out for about 30 seconds then back to cold. called chevy dealer they think its the door actuator (in cabin/fresh air). doesn't really make sense to me. Has anyone else had this problem? if so what have you figured out about it if anything? Any signs or symptoms you've noticed with this issue? Thanks.