Ok I have no heat in 1999 jeep grand cherokee limited. I replaced the heater core, blower motor and blower motor resistor. Cannot figure out what the problem is

There are two systems to evaluate.

1. Air Blows Fine but not Hot -> Check Thermostat and coolant level.
2. No Air Blows -> Check Blower Motor, Blower Motor Resistor Pack and Blower Control in Dash

bingo !

http://www.fixkick.com/look/odds-ends/jeep/2000GC-heater-motor.JPG

check the heater core

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Blower Motor Resistor and Controller Replacement

Image Blower Motor Resistor Or Controller/Power Module Remove/Install

REMOVAL

1. Disconnect and isolate the batten' negative cable.

2. Depress locking tab and unplug the wire harness connector from the blower motor

resistor or controller (power module).

3. Depress locking tab and unplug the resistor or controller connector from the blower

motor.

4. Remove the 2 screws that secure the blower motor resistor or controller to the

heater-AC housing.

5. Remove the blower motor resistor or controller from the heater AC housing.

INSTALLATION

1. Install the blower motor resistor or controller to the heater AC housing. The

housing is indexed to allow (controller power module) mounting in only one

position. Tighten the mounting screws to 2.2 Nm(20 in. Lbs.).

2. Plug in the wire harness connector to the blower motor resistor or controller.

3. Plug in the connector from the blower motor resistor or controller to the blower

motor.

4. Connect the batten' negative cable.

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Regards, Lee Davidian

under the dash on the passanger side. its mounted in the heater box

the blower motor resistor is bad replace it and it will work good as new the resistor is located in the same heater box as the blower motor mounted on the outside of the heater box follow the wirring from the blower motor to find it or just simply buy the part and match it up

most likely the blower motor try tapping it if it makes a noise or starts blowing a replacement is necessary

It sounds like the blower motor is not working. If you don't hear it running when you switch it on, check the fuse first. If the fuse is OK, you will probably need a new blower motor. It could also be a faulty fan switch or blower motor resistor. Once you remove the blower motor assembly, you can test it by putting battery voltage across the contacts with jumper wires, making sure to get correct polarity. If it does not spin, it should be replaced. If the blower does work when removed, the fan switch is probably at fault. The resistor is usually indicated when the fan works only at certain switch positions, but not all.

2 problems?
No blower motor: Blower motor resistor very common or motor itself or heater controls.
No heat: Start simple with check antifreeze level after vehicle has sat for a few hours. If that's OK then it could be thermostat, heater controls, blend doors, water pump, restriction in cooling system

Change your Thermostat.