my 99 ram 2500 V10 quite blowing hot air could it be a cracked vacuum hose ?

 

Check coolant level first.

Then, with the engine at operating temp, and the heater cranked up on hot, check the hoses to/from the heater core, they should both be pretty flippin' hot.

What happens when you run your temp **** from one extreme to the other? Do you hear the blend door thump at both extremes?

 

the vacuum lines that run the heater control are on the pass side firewall and run thru it, very brittle and easy to crack, if it won't cycle from floor to defrost to panel, etc, that's the prob, otherwise mine is doing the same thing, i narrowed it down to the heater core....rather than replace it i opted to run 120 psi thru it and force flush it ( with both hoses disconnected from the engine!!!!) i got temporary relief, i will try letting a chemical soak in the core next ( fill the core thru a heater hoses, let it sit then blow it out again, but i def could just be low coolant!!!! listen for a gurgle in the dash = air in heater core