2001 GMC Sonoma.
Maximum air temperature from heater is 65 degreesl. It that right or should it be warmer? Engine is normal temp.
No, it should be a lot hotter than that, you could have a fresh air blend door that is not working right or a plugged heater core, you might check the heater hoses when it is at full operating temp and see if the hoses are both quite warm to the touch, if one is hot and the other noticeably cooler then the core could be plugged. HTH