I have had beautiful heat in my truck for the 13 yrs I have owned it and now it is gone. On the coldest day of the year air just blew cold, at the time upper radiator hose was hard as a rock so I figured thermostat. I changed it with motorad from advance auto and barely had any heat still so I bought a mopar one which is motorad anyway and still barely had heat I flushed heater core which was clear and checked my blend doors which are still intact but I changed the actuator anyways I also purged the system of air which seemed like forever. I decided to change thermostat again with another mopar one because it seem when I am on the gas I get better heat which is a sign its thermostat related and it turned out when we tested second one it didn't open. So as of now I barely have heat. Water pump was done in June or July and cooling system was changed from and degasser type to radiator with cap type 2005 style about 1 yr and a half ago. Thanks for any input

 

You still have an air pocket in the heater core. That's why you get better heat when you are on the gas.

 

I noticed last night I had full heat out of defrost but cold air out of everywhere else. I was told to look up under driver side to find the mode door actuator and door that controls where the air blows out. I thought there was only 2 doors but was corrected that there is 3. Keep you posted

 

Hey Kevno6,
How is your heater core? Pull back your carpet on the passenger side front and stick your hand down there to find if it is wet. I just rebuilt my 2006 Ram 1500 Mega Cab HVAC box last weekend (12/16).
Any smell of anti-freeze in the truck?

 

no smell of antifreeze and carpet is dry. It has to be the door that controls where the air blows out. When I have it on defrost the is still some air blowing out by feet but its cold and vise versa. just have to get behind radio to see because that's where it is. Just too damn cold to do it now.

 

Yeah, but, when it's warmer out, it isn't as much of an issue, so you are less motivated to work on it. (yes, I fall into that trap as well......)

 

A failing heater core will not always cause the carpet to get wet. Remember, the HVAC box has a drain for the A/C condenser, so a leaking heater core will follow suit. The smell of coolant or fogging windows are more accurate indicators. As the OP noted, he has heat in one scenario but not another, which means it's a diverter issue.

 

I check all 4 actuator and they all work but I didn't get in deep enough to find out if diverter doors are actually closing all the way. What's making me thing they are not is when I have it blowing full floor there is still air coming out defrost and vice versa. Like I said full heat from defrost but put it to floor just cold air. Thanks for the suggestions

 

I would think either the heater control module or wiring. Since you have heat with defrost seems like your heater core must be good. The actuators all works it just seems the blend door does not go into the correct position when directed to floor or vent.

 

Hwy Gary. While I agree, I will add that when the core is bad and leaking, the coolant does not always drain. It will find its way through the entire box, therefore it will make its way out in other ways. When I opened the box, there was puddles of coolant in every section. Maybe it depends on the severity/length of time the care was bad.