My truck is a 2004, since I have it the heater is not blowing a lot of heat during winter, this not realy a problem for me but my wife and my kids dont realy like the cold. I change the thermostat, I put a rubber mat to close 75% of the rad, the T is rising like normal but the fan is blowing cold air most of the time. Where I work I drive some newer cummins, 2006, 2007, and they blow heat like hell, the T just start to raise and the fan blow hot air. I dont now if some door in the blowing system are broken or what, last summer I check if the motor move the door when I move the control and everithing was looking fine, Yesterday it was -35 C here in Canada and the cab start to warm up after 1/2 hour drive... dont now where to check next...

Either the heater core is plugged up or the blend door is not operating properly. If the heater hoses are both hot then the heater core is plugged up. Normally one of the hoses should be a bit cooler that the other.

I will check that, is it a problem on this model that the core get pluged.... I never have any problem like that with any of my other truck.

It really common for those people that never change coolant till the coolant is rust or discolored. As for me I change coolant every year and flush the block. I usual catch the ones complaining about heater core issues haven't change coolant in many years or hundreds of thousands of miles...

If it throws no heat... and core not plugged, then blend door / actuator. PITA to get to but could well be just the coupler. Located over the passengers footwell. http://forum.mopar1973man.com/threads/4612-Before-you-replace-a-non-functioning-blender-door-motor-actuator!!!!?highlight=heater+treater http://forum.mopar1973man.com/threads/3560-Damm-Dodge-Diverter-door!?highlight=heater+treater If it blows on defrost (default mode) then the vacume control on top of heater box is defective. Dash has to come out to get to, to right of Go pedal on top of heater. My nephew was able to put fingers on mine but it went back as soon as I started up. I'd like to know how to wire it in place sometimes.

good info

I had this problem with my 04'.5, looked at everything you did and changed the thermostat and always keep the anti-freeze up to date. What it ended up being was, actuator doors. If the actuators work, the flapper doors can be the problem (as in my case) where the shaft had split and the door would fall back to closed position from an open position. Complete removal of the dash required! What a pain this was. I have the doors temporarly in the open position for now.

The blend door coupler is a PITA to get to but it can be done with the dash in. It's on the passengers side of the hump & requires on the sec gen, to have the rubber floor pad under the rug cut away for clearance. The stupid plastc coupler is prone to crack & split. A reinforcing sleeve can be turned & pressed on in a vise or a new part made.If the air only blows on defrost, then either the vacume is lost or the vacume actuator to the right of the driver's side is broke & does require the dash to be laid on the seat.