I had a similar problem. But I never got much more than cool air. If you are randomly getting warm air and then not again for a while I would automatically think heatercore. Especially if the truck is running right and not overheating. For me it was a broken blend door. Go to http://www.heatertreater.net and do some homework there. I have an 09 2500 (gen 3). This fix was a 2 day ordeal for me that involved removing the entire dash, but will be vastly more simple for you with the early gen 3 dash. That is, if this is indeed the problem. You can verify whether or not the blend door is your culprit by taking out the glove box. Look on the left side of the opening. You should see a 4 inch(ish) metal guide that is attached to an actuator. Its about as thick as a pencil lead. It will be the only metal looking 'wire' in the vicinity. That guide operates the second blend door in the series. Oddly enough there are two. Adjust the blend **** and see if that guide moves up and down in a definitive motion. If not, your main blend door is a gonner.
Watch the heatertreater videos on their website. They are very informative if this indeed ends up to be the problem.
Good luck.

 

The metal piece that you're tapping about is the damper linkage that links 2 dampers to 1 actuator. That is found only on single temp. control buggies. On a two temp control, that rod is eliminated, and another actuator is added, which I believe hides behind the hvac box.
the rod moving only shows that the actuator is functional. The dampers themselves, or the damper pivot(s) could be fubar.
single temp = 4 actuators.
two temp = 5 actuators

 

so they can charge us the 10-12 hours of labor they say it takes lol. but yes that would be the smart thing to do

 

UPDATE!!!! GUUESSSS WWHHAATT!!!!! Myyy ****in heat doesnt work again!!!!!!!!! im so beyond furios idk what to do right now. im seriosuly about to go light that pos on fire!!!! absolutely fed up!!!!!! heat has worked perfect for the past 3 days since i replaced heater core, now its ice cold!!!!

 

Let's not jump to conclusions. Is it possible that the core has become air bound?
Start, once again, at the beginning of diagnosis. Are the heater hoses getting hot? Is the engine up temp? Has the t'stat failed?
Aggravating? yes. but, it is a machine. You can figger it out. You have already done so once.

 

tstat is brand new as is the water pump, radiator, clutch fan and serp belt and rad cap also. truck runs perfect right where it should so its not any of that. air is all i can really think of. a few ppl said to try to park it on an incline so the front is up higher and just run it with cap off for a while and see if i can burp it out. thats all i could really think of. didnt check heater hoses as i was so pissed as soon as i got home i went inside so i didnt beat the hell out of this truck lol

 

so just went back outside and got the truck on an incline with the nose up, popped rad cap off and let it run for 30 mins revving it here and there. truck was all the way warm and no heat again. heater hoses were both hot, rad hoses were all hot and the recircualtion tube going into radiator tank had perfect flow. one thing i noticed is that on defrost it was much warmer then when i set it on the vents. i still have not had my a\c system charged either. all i can say is i have a nasty air pocket in the system somewhere. i wonder if it would be worth it to bring it to a garage and have them completely flush coolant system. it has all brand new coolant in it i used peak 50\50 that had the additive for chryslers. im just beyond stumped and dont know what else it could be besides air in the system or something got sucked into my new heater core and is blocking it up.

 

I haven't kept up with your posts.
did you flush the coolant circuit with the proscibed amount of cleaner when you began on this problem?

 

no i have not flushed anything since the heater core was installed. im wondering if i should just have the entire system flushed at a garage. i have more people telling me its my blend doors again

 

well, both hoses are hot.
you have flow then.
blend door............ one or 2 temp control?