Air flow out of A/C (HVAC) seems to be partially blocked. Noise increases with increased fan speed settings, but flow barely changes. Even on maximum setting the flow is not enough to reach driver or passenger in the front seats. It is only just noticeable at about 6-8 inches from the vent. This truck had great A/C air flow until maybe the last year or so of use. All driving is on paved roads, and the truck has just over 50K miles on it. Does this system have a cabin air filter, or is it likely that something disconnected or is lodged in the ducts? The control that diverts flow to upper/lower vents, recirculate, and defroster vents seems to work normally.

There is a little motor on the heater box under the dash that needs to be replaced. It's called a blend door actuator...

the heater has dampers, and the mode section is sticking
the tests are in the FSM. under HVAC
see YJ here

http://www.jeep4x4center.com/knowledge-base/index.htm?utm_source=cj#service

there are 3 systems used, cable, vacuum, and motors.
in cable and vacuum , you only need to look to see if the actual damper lever works.
if yours is motor, its way more difficult. look in the FSM for that test.

ac evaporators inside a car become useless f the evaporator fins are blocked with a black greasy gunk
It will stop air flow from the blower motor and will not allow the air to be cooled as it passes through the fins
It is unlikely that there is a blockage in the vents
if a section of the ac evaporator box can be removed , check with alight and mirror to see all the fins are clean and if not , use an ac fin cleaner product to melt the gunk of the fins

It could be that; the FAN MOTOR works but the fan-wheel is not turning. This usually happens when the center spindle of the fan-wheel RUSTS and eventually loses contact with the actual wheel itself.

My suspicion is that the fans may be coming on but they are not picking up speed when you turn on the A/C. Your car would have some of relay to control the speed of the fan whenever the A/C was turned on. This relay system would also increase the speed at which the fans run when the engine heat turns them on too.

Try starting the car cold and turning on the A/C right. Even though the engine is cold the rad fan should start up when you switch on the A/C. Once the engine gets hot the fan speed should increase accordingly when you switch on the A/C.

I'm not familiar with how Chrysler makes this work so I'm unsure what to repair but this is most likely your problem. Hope this helps.

when it's on 'auto', the fan adjusts according to the temp in the car and the temp setting you have it set at. try setting the auto temp control down to 65, then hit the "-" one more time to send it to "LO" - the fan should automatically jump up to max.

Though too much fuel can do that, it virtually always is not enough fuel at the transition to the more-open throttle setting.

You can also get his from
a vacuum leak
the float level being too low.
the main jets being partially blocked.
a defective accelerator pump (ruptured diaphragm, bad lip seal, etc)
a disconnected accelerator pump (though that is usually worse than you describe)
an accelerator pump not set to deliver enough fuel.

When you move to a higher power, the required increase in fuel flow takes a half second or so to get established, because fuel has mass; it cannot just suddenly flow faster. The accelerator pump is there to squirt fuel into the airstream as if from a squirt gun to cover the brief lag in flow response. (That's all it does. Increasing the flow of that pump past optimal does not increase power, it reduces it, making the response just a little more sluggish.)

under the dash on the right side ,look for a plug with 5 wires . That switch is called a RHEOSTAT.(fan speed control).Sounds like it is defective

The shroud around the radiator fan mainly assists cooling at lower road speeds - it increases the efficiency of the cooling fan/s.
At higher road speeds the increased airflow due to vehicle speed makes the fan and shroud less important in that circumstance.

Running hot at higher roadspeeds can be caused by either engine mechanical fault (blown headgasket etc) or defective cooling system:-
Check for combustion gas bubbles in coolant reservoir - and ensure engine has no other mechanical running problems.

Check cooling system as follows:-
1) Faulty thermostat,
2) Blocked radiator air flow due obstruction such as grasshoppers or other insects,
3) Blocked radiator core (internal) by sludge/scale etc.
4) Collapsing radiator hose on intake side of waterpump (due to softened hose),
5) Cooling system not properly filled with coolant due air locks in the system - bleed off any air (as manufacturer specifies) during re-fill with coolant and ensure flow to heater core is enabled.

Classic signs of a bad water pump. When on the freeway, the circulation of coolant through the system is increased due to the speed but once you slow down, it will tend to overheat. Please post back with any other questions or just to rate the solution. Thanks very much!
Greg