I have a 1997 V-6 3.9. I am having a problem getting heat. I can feel heat on my feet, when I don't have the fan blowing, but as soon as I turn the fan on I get cold air out. I only bought the truck in July, and noticed even when I turned everything on the heating/cooling system off it still blew cold air. Now that it's getting cold here (NY) I need to figure this out. Stopped at Autozone yesterday and the guy said I might have to have the computer recalibrated?. Any help would be appreciated.

 

Forget the guy at Autozone, makes no sense. My guess would be the blend door. The blend door is what changes the temp from full hot to full cold and what ever in between. If the blend door has broken loose, the fan my be pushing it closed towards the cold side, giving you cold air whenever the fan is on, warm air when the fan is off. My first guess.

 

Moron at Autozone.
Blend door is my bet also.
I would start 1st by checking all the vacume-lines
under the dash to see if one got yanked out by mistake.
Then look behind the control-panel.

 

LOL!

I went to Autozone one time to buy a freeze plug for my Camaro- dude told me i had to get one from a junkyard!

I said..."uhhhhh", turned around and walked out...

 

Had the same issue. Took apart the dash. On my 1997, the heat blend door is mechanical, so it's really tough for it to fail. It runs off a cable connected to the temp control ****. Mine seems to be fine. I then took the heater hoses off the engine and flushed the heater core with my garden hose. It seemed to help, but I still think I don't have full heat. Computer????? LOL!!!!!

 

Automatic temp controlcan be calibrated; that is done by holding certain buttons. Usually if there is a problem, the lights on all the buttons will flash. I've never seen a Dakaota with this type of HVAC panel. Only Caravans.

Anyway, your problem sounds more like A) the aforementioned blend door issue or B) the heater core is clogged/low on coolant and the increased airflow from the fan is cooling the air faster than the core can warm it. Check your coolant level in the radiator and reservior. If that is OK, flush out the heater core with a hose (both directions). When done, replace one of the heater hoses and clamp off the other. Fill the system until it pours out of the exposed core port. Replace the other hose, top it off and let it get to OT. Then shut it off and allow it to cool, and re-check coolant level.