2003 379 heat ?

Mine has 4 valves (Cummins) My brother-in-laws has 5 valves (Cat)What does "really don't" mean? Is it luke-warm comming out of the vents, or is the air at the vent hot but won't warm the cab? What is the outside air temp? If its 40 and you can't take the chill off you've got a problem. Make sure your fresh/recirc door is closing tight.I've got a million more questions but lets start here.

 

My 2000 379 ISX had 2 valves side by side on the pass side rear of the block, and 1 on 1 of the heater hoses up by the water pump,and one down inside the frame rail up front by the bottom radiator pipe(really hard to see/get to). But all that said,if the vent temp is changing that much your fresh/recirc door is definatly open, you can see the door open and close if you take the cabin air filter out and kinda stand on your head to look into where the filter came out of and move the switch from fresh(open) to recirc(closed). And it sounds like your water flow to/in heater core is restricted pretty bad, if all valves are open then I woud look at cleaning/changing heater core(s).