I have a 1999 Jeep Grand Cherokee The blower motor for the heater & a/c will not come on with the auto temp control but I can put direct 12 volts to blower motor and it will work

1998 ATC Jeep Grand Cherokee Blower Resistor connector ...

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www.youtube.com/watch?v=sDFLuenx9aw
Nov 14, 2012 - Uploaded by Freedomautomotive1
1998 ATC Jeep Grand Cherokee Blower Resistor connector Repair Kit (RARE 1/2 Year) ... How to Fix a Chrysler Blower FanThat Only Works on High - Duration: 16:51. ... JEEP2001 FIXING THE HEATER BLOWER CONTROL. ... Jeep Grand CherokeeCenter and Lower Dash Removal - Auto Repair Series ...

Usually you have to splice the wires into the old plug.
You might be able to find a diagram on the websites for auto parts stores such as autozone.

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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.

Thank you for using FixYa.com

Regards, Lee Davidian

I had the same issue. It turned out that one of the wires had burned out and therefore the connection would not hold. The dealership had to replace the wire and the connection point. They said that it is a manufacturer problem, however, generally it takes about four years to fail...so they don't have to replace it.

Could be module check with the dealer where is.

UNPLUG BLOWER & HOTWIRE TO A GD 12 VOLT BATTERY... LET,S DETERMINE IF THE BLOWER IS ANY GD...CHARLIE

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

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

Are you saying that the switches are bad?
Or that when you turn the blower on and select a different temp. it doesn't change temp.?

if it only works on hi...the resister is bad on regular ac heater systems or on auto temp control systems the powern module is bad.....if it is totally inop then likely a fuse or bad motor