Heater Issues

[hoosiermichael75]

2006 KJ 3.7
This fall the jeep started blowing no heat. It has a burst of heat when the blower is first turned up. Then cool air. Blend door seems to be working as you can hear the system switch from cold to hot. Blows cold when switched to cold, blows ambient temp when set to hot. Mode door seems well also, as it will blow out whatever vents it is directed to. Lower radiator hose stays cool to the touch. Both heater hoses get hot. I just flushed the whole system and refilled, adding a new thermostat (old one tests good). Now the lower radiator hose gets hot as it should, I believe. And I am now blowing some heat from the vents, about 101 degrees. But if I switch the mode to defrost, it goes cold. Defrost/feet blows cold. Feet only blows cold. Vents/feet blows cool. Vent only: 101 degree heat. This, I can't understand. How would a mode change effect the blend? Temp gauge before flush and now always steady at the halfway mark. AC overriding the heat in defrost mode? Maybe I should reflush the core?
Any help would be appreciated before I tear into the dash to get to the hvac unit!
Thanks.

 

[ltd02]

From your description I'd say your heater core is plugged but couldn't rule out the possibility that the blend door isn't moving properly. Since you said you could hear the actuator, I'd assume that isn't the problem. The core really can't be flushed due to its design.

When my actuator went it would only go smoothly from hot to cold. If you put it all the way to hot occasionally it would but usually it would only get slightly warm then it quit even getting warm altogether.

 

[LibertyTC]

It could also be trapped air in system, can take a few days, use bleed screw,top rad hose housing.
When Hot, slightly loosen till air bubbles come out with coolant, and close it.
I place paper towels below, before I opened it.
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Note the Mopar thermostat has a air bleed hole which helps, did you use the Mopar one?
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Overnight when cold, monitor the reservoir tank and keep it full to the middle.
It can take a few days of hot/ cold air bleeding, to get rid of air in system.
I assume you only used HOAT or Zerex G-05 for coolant if not, flush time again!
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Do a reservoir pressure test to see if air is entering system as well or if leaks suspected.