HEATER STAYS IN DEFORST MODE NO MATTTER THE SETTING

Sounds as if the problem is in the climate control panel. The panel may have a bad circuit board that is dropping signals to the components you are trying to operate.

no year, no joy, posted that 100 times.

the ac compressor cycles when you have the defrost on that is the clutches on the air compressor

a couple of things,1 blower motor fuse.2 blower motor gone out.3 switch on fan speed control switch not sending signal to fans.after checking the fuses.next check theswitch on control panel.set ac or heater.if fan still doesnt come on then replace it.when it work and then stops working there are a lot of possiblities that caused the prob relay too not fliping over inside staying close loop.hope this helps.

since your buddy is a Chrysler tech, he should know that the heater module can be recalibrated with the scan tool or pull the POSITIVE cable off for five mins and put back on restat the car and select all modes, I assume this worked prior to batt replacement, sevice manual helps you do a manual calibration in different modes. GOOD LUCK RDJRP

I found a broken vacuum hose on top of the intake which runs the controls

when your car is in defrost it has an ac cycling it removes the moisture then sends the air over the heater core depending on how warm you set it you can feel warm or cold but the ac is always cycling...ridding the moisture...you need a good ac tech it will be okay...its just expensive going into the heater core if needed...!

It sounds like you have a bad temp door actuator.

you need to begin by changing the thermostat. if you dont know how go to an autozone and they will assist you.

if that doesnt solve the problem you need to change the heater/ac blower relay.

The heater controls would be the first thing I would check, and then the actuators for the mode door(s) would be the next. There should only be one heater fuse.