hi i bought a 2003 dodge cummins diesel 1 ton dually 4x4 automatic 150.000miles, everything works perfectly, except for the heat, i dont seem to get real nice heat out of the vents, even though i travelled 200miles yesterday ! thanks for ideas

 

Check this thread, you may have the same problem (I do )

https://www.dieseltruckresource.com/....html?t=170393

 

That sucks... Hope you got a good deal on then. Looks like you have reading and fixing to do.

 

Pop the hood and see if someone installed a shut off valve in your heater hose.