1998 Blazer 4wd 4 door
Never had this problem on any of my cars. I put the heat on the lowest setting. I think it’s 66 degrees, one degree above horizontal. When it warms up, it feels over 70, maybe 75 to me, regardless of the temperature outside. My shop checked the temperature, its normal, said there are no vacuum line leaks. Normal?

 

I'm not sure what the problem is exactly, is it blowing warmer air than you'd like or do you feel it's not turning off at the correct temperature? If it's the latter, the ambient air temperature sensor you're looking for is behind the radio to the right in the HVAC duct I believe. The zero dollar fix is to crack a window and draw some of that warmer air out or just manually turn off the fan itself.