So during this last cold spell, my heater has almost completely quit working. It blows cold while at idle, or normal driving. I can accelerate pretty hard and it will blow hot for a few seconds, then back cold. I've read about the actuators on the blend doors being an issue, but seems to me it would never get hot if this was the case. I'm kinda stumped, an looking for any other advice on what to check!! My truck is a 2012 lariat, dual climate. Thanks in advance!!

 

Truck is warmed up? Does your temp gauge stay steady? Is it on all settings?

 

check your coolant level