Fan blows but no heat - 2001 Dodge Ram 2500 Truck

Sounds llike vaccum problem with the heater 'doors' which switch directon of air flow.

Sounds like high blower relay is bad

no fan, on high? or no heat , fan at full speed.
if fan blows , it can only be 2 things,
1: engine not at 180F or holding.(min, temp)
2: water valve or damper stuck. (and there respective controls)

Sounds like a possible water pump problem with the over heating part. About the heater only blowing cold you may have to get it "recharged"

Your airconditioning system may be out of cooling gas, and if it has sufficient gas, the compressor might not pick when you put on the AC, and if the compressor did not pick ie start, you cant experience cooling effect, the fan will only be blowing.

There are a few thing that can cause the heat not to work, this all depends on what you mean by no heat, is the fan blowing air but not hot or is the fan not working at all?

i will say to heat the coolant level in radiator and make sure it is full, this is if fan blows but not hot. let me know, good day

your radiator in the car is fool of slam

To prove the valve that gives water pass towards the heating if this one does not open you have no heating inside the car

Several things ... best guess, in order:
1. (very likely) Radiator fan is not blowing (turn on car and a/conditioner.
When compressor kicks in, the radiator fan must blow). If it ims not blowing,
the radiator fan motor may be burned out ($40).
2. Check / replace "cooling fan" fuse ($1) and / or "cooling fan" relay switch
($7).
3. Radiator clog (possible)
Hope this helps!

That shouldnt be a problem. I have a 99 Sebring and it does the same thing. it has never overheated. if it is only blowing small amounts of heat you should be alright. and the fan is blowing to prevent the car from overheating.
having a heater running will help a car from overheating, it actually helps cool the engine.