Blowing Luke Warm Air

[bigfat66]

i have a 2006 sliverado crewcab duramax with auto temp control after driving for a while it will start blowing cold air i have replaced the thermostat and blend door motor any suggestions

[jro909]

is it running cold? heater core sound?

[bigfat66]

IT RUNS AROUND 195 HEATER CORE IS GOOD

[ChevyTech77]

Are both heater core lines hot?

 

I've found a TON of connection issues at the right side dash junction blocks. They are accessible on the right side

of the dash behind the dash end cap panel.