I have a 05 3500 and the heater will work fine for months and then stop working for a couple weeks and start working again like nothing was wrong. I feel as if something is loose. Once before while driving down a dirt road it wasn't working and i hit a nice size hole and it came on....Any Ideas.....FYI...i checked the recirculator door and it was fine

 

If it's intermittent like that, could be hard to figure out. But I would focus on the actuator for the blend door, possibly a loose connection. Unfortunately, kind of difficult to get to. Are you getting air out of all vents on the appropriate settings? I don't think you have a broken blend door, as you wouldn't have heat no matter how many bumps you hit!! There are tons of threads on this subject, especially this time of year.

 

Its not just the heat ...its the A/C as well...its a year around thing. Air does come through all the vents but very very little

 

So............ your issue is air flow?
check the recirc door to see if it is intact, not laying on top of the blower inlet.

 

Is the blower operating appropriately at all speed settings, is it making noise?

 

It would help if you provided more detailed information.

 

X2........

 

The door is fine..1st thing I checked...my issue is the air works when it wants to...it will work fine for months and then stop for 2 or 3 weeks