Hello- My 2001 Siverado 1500 heater is acting up. A year ago I flushed the heater core when this happened. The heater doesn;t blow hot air....it gets luke warm and warm enough to get defrost the windshield but not comfortable to drive. Does anybody know if these heater cores have a tendency to "gunk" up after an initial problem? Or could it be anything else? Thanks!!!

 

Once it clogs for the first time it is prone to happen again. Is the temperature gauge reading hot? If not you may need a t-stat.

 

Temp reads normal. I put a new t-stat in about a year ago. Looks like it may be a long night in the garage so I don't have to deal with another cold MN morning