Heater Issues

2008 DCSB: Most mornings I start my truck about 15 minutes before I have to leave the house so It can warm up, when i get in my truck about half the time it will be blowing hot air by the time I get in. Other times it is blowing ice cold and It takes a few miles of driving to start blowing hot even though the temp gauge is showing that it should be blowing at the very least a warm air.. About 15 miles from my house is a red light that I have never been able to catch at the right time and every morning when I let off the throttle to stop at the light the air starts blowing cold again... Do the air blend doors work off of vacuum? If so can someone recommend what lines to start checking first? If not what else could it be? I swapped out my ac control panel (all three switches) with a buddies to see if that made a difference and it did not..

 

Bump!

 

flash heater core
http://youtu.be/LD2LGkUycQg

 

No reason to pre heat the truck. I climb a slope after starting and warm within 90 seconds, blowing hot air, mostly because I am working the engine. Stoping at a red light after start will make it cold fo sho

 

I spoke to a mechanic yesterday about what was going on, he recommended a core flush as well..
My house is right on a major highway and the speed limit is 75, it takes my truck a good 5 minutes for the temp gauge to get to the normal operating temp, I'd rather go out and start the truck before I start getting ready so that when I get in my truck it is already warm in the cab.. I really dislike wearing jackets and hate having to wear one to leave the house and trying to pull it off 5 minutes later. I start it cause i'm a wus when it come to the cold, not for the old myth of not driving until it's warm.. lol