The heater/AC fan makes a clicking sound when it is in deforst mode.

Leaves in the heater motor area? Or possibly may have sucked some paper into the fan motor when AC on recirculate mode

give the parts store the make and model and they should print the instructions out for you or look it up on line...good luck..

I doubt if you have a fan problem. More than likely you have a bad actutor motor. There are 2 small electric actuator motors under the dash. The temperture door actuator moves the air temperature door, which controls the temperature of the air coming from either the a/c or heater vents. The mode actuator (which is probably the one you hear clicking) controls the mode of operation, or more simply, which vents the air will be coming out of. When the internal gears of the mode actuator fail and start slipping, they make a loud repetative "clicking" sound, which is what you are hearing. Another symptom that may or may not accompany this situation is a longer than usual wait time for your mode selection to occur. So to sum up, a loud repetative clicking sound from the center of the dashboard possibly accompanied by a longer than usual wait time for your ac,heat or defrost mode to occur, usually indicates a failing mode door actuator.

is some coming out deforster or floor?

Do you have a cabin air filter?

Does it come out better in MAX a/c mode?

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.

You need to replace the heater/AC blower motor the motor shaft bearing is defective..

the motor that opens the vent is stuck. Put in it fresh air mode. the vent should be on the pass side behind the glove box. Take off the glove box and disconnect the motor and replcae it. Or the cheap way is to not use that mode

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

Sound like a vacumm leak at one of the baffle door controlers. Look at heater box when makeing noise, should be able to see which controler is going in and out. Once you isolate which is the culprit check the hose circuit for that door.

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...!