So the thermostat was replaced last year and didnt really seem to fix the problem. I own a 99 durango and the heat really sucks in it. And it seems when i turn on the fan my temp gauge drops aliitle. What is going on. Amoung that not that it is a big deal but when i switch from face to floor it never completly stops it fom coming out on the face vents and defrost there is always some air coming through. Apprieciate any input

 

You may have an issue with your blend door/stuck air valves causing the exfil on only windshield/face. Also if that setting is cold when on hot you may have a plugged heater core.. Most mech will let the truck run till warm feeling the two heatercore lines for difference in heat. I'd recomend flushing your HC, but thats just for heat and wont solve your vent issue being the dash may have to be removed

 

If you change the temprature **** to full cold does the air get cold? If you move the temp **** and the air tem stays the same there is probabnly an issue with the blend door. If it does change temp then your hearter core may not be getting hot enough in which case it might be clogged.

 

i agree with what brad said, it sounds like your directional doors (face/floor/defrost) are jammed, or the vacum line which controls it has come off or is cracked/leaking, and if the temp changes a little when you slide it from cold all the way to full heat it is most likely a plugged heater core, PITA to change unfortunately

 

When i turn the **** to cold it comes out even colder so that is working.

 

Well have you tried to flush your heater core?


Also, check you vacuum lines for cracks.

 

the temperature controls are cable actuated, the output controls are vacume (switching from defrost to floor to face) i think you misunderstood before

 

I don't mean to hijack the thread, but I have same issues on 98 durango. Flushed heater core today and no better. I got a Prestone coolant flush kit from Autozone and tapped into the line on the passenger side. Had to hose clamp a cap on one end but it worked fine. Then I took the driver's side line off the water pump and emptied into a 5 gallon bucket. I get plenty of flow through the heater core. It was pretty murky at first but eventually ran clear. I then switched it up and flushed out the other direction, and I get plenty of volume.

I also had the issue with only blowing out the defrost vents on the windshield. The vaccum line going through the firewall just under the heater core was snapped. I was able to use a rubber coupler with some silicon and the vents change like magic now. Except it's still lukewarm!

After getting the truck up to temp, the heater core line on the passenger side is real hot. The line on the drivers side feels less warm. Assuming that passenger side is feed, then the heater core is working and dumping the heat somewhere, it just doesn't make it to my feet. If I have the flow direction wrong then it suggests plugged core. I have read that if both hoses are not hot, then it must be blend door. I can watch it flush out both ways so I don't think it's plugged.

I have also read that there is a blend door that switches between heat and A/C/. Is this different than what controls which vents blow? Seems I found another post but can't find it now about someone who had a cam slip out which controlled a blend door. Does that ring true? Really hoping to avoid tearing the dash out.

 

i know this might sound crazy, but make sure you have enough coolant in the system. you might have an air pocket in the system. if you do you will only get lukewarm air. an easy way to see if your heatetr core is full of coolant is to start your vehicle, turn off the radio, fan and any thing else that makes noise inside, then bring your rpm's up a little. if the core isn't full you will hear a gurgling noise because or the air in the core. if you have this noise bleed the cooling system.

 

you are pretty well informed on this and everything else, the blend door for the heat/ac temp is cable controlled and is different than the blend doors for the direction so you could have a jammed or busted blend door not allowing enough air to flow across the heater core . . . unfortunately that is a pita to find in the dash