This is a common failure on 1999-2004 WJ models with the AZC (Automatic Zone Control) system. The connector on the blower motor control module overheats, resulting in intermittent or no operation of the blower motor. Mopar released a connector harness repair kit to fix the problem. The damaged connector is cut off and new wires are spliced into place. Only the green wires from the kit are used. One end of each of the 3 green wires goes into the new connector end that is provided. When inserting the wires into the connector, the locking spring tabs should be on the bottom. There is a gray plastic retainer that is then installed around the three wires that were just inserted into the connector.
The part number for the kit is 05102406AA and the MSRP is $19.65.
Some owners have elected to repair the wiring by soldering wire splices directly to the terminals inside the blower motor control box and not using a connector.
Additional blower motor information and diagnostics
- Manual temperature control system
Models with the standard manual temperature control system have a BLOWER MOTOR RESISTOR. The blower motor resistor is mounted to the bottom of the HVAC housing, under the instrument panel and just inboard of the blower motor. It can be accessed for service without removing any other components.
The resistor has multiple resistor wires, each of which will reduce the current flow to the blower motor to change the blower motor speed by changing the resistance in the blower motor ground path. The blower motor switch directs the ground path through the correct resistor wire to obtain the selected speed.
With the blower motor switch in the lowest speed position, the ground path for the motor is applied through all of the resistor wires. Each higher speed selected with the blower motor switch applies the blower motor ground path through fewer of the resistor wires, increasing the blower motor speed. When the blower motor switch is in the highest speed position, the blower motor resistor is bypassed and the blower motor receives a direct path to ground.
The blower motor resistor block cannot be repaired and, if faulty or damaged, it must be replaced.
Models equipped with the optional Automatic Zone Control (AZC) system have a BLOWER MOTOR CONTROLLER. The controller allows the selection of almost infinitely variable blower motor speeds. The controller is mounted to the HVAC housing, under the instrument panel and just inboard of the blower motor, in the same location used for the blower motor resistor on manual temperature control systems. It can be accessed without removing any other components.
The blower motor controller output to the blower motor can be adjusted by the blower motor speed switch knob on the AZC A/C Heater control panel, or it can be adjusted automatically by the logic circuitry and programming of the AZC control module. In either case, the AZC control module sends the correct pulse width modulated signal to the blower motor controller to obtain the selected or programmed blower motor speed.
The blower motor controller cannot be repaired and, if faulty or damaged, it must be replaced.
Blower motor switch - description
The A/C Heater blower motor is controlled by a rotary-type blower motor switch, mounted in the A/C Heater control panel. On vehicles with manual temperature control systems, the switch allows the selection of four blower motor speeds, but will only operate with the ignition switch in the On position and the A/C Heater mode control switch in any position, except Off. On vehicles with the Automatic Zone Control (AZC) systems, the switch allows the selection of Lo Auto, Hi Auto, and ten speed settings between Lo and Hi.
On manual temperature control systems, the blower motor switch is connected in series with the blower motor ground path through the a/c heater mode control switch. The blower motor switch directs this ground path to the blower motor through the blower motor resistor wires, or directly to the blower motor, as required to achieve the selected blower motor speed.
On AZC systems, the blower motor switch is just one of many inputs to the AZC control module. In the manual blower modes, the AZC control module adjusts the blower motor speed through the blower motor controller as required to achieve the selected blower switch position. In the auto blower modes, the AZC control assembly is programmed to select and adjust the blower motor speed through the blower motor controller as required to achieve and maintain the selected comfort level.
The blower motor switch cannot be repaired and, if faulty or damaged, it must be replaced. The switch is serviced only as a part of the a/c heater control assembly.
Blower motor diagnostics
1. FUSE: Blower motor power feed circuit fuse may be blown.
2. COLD ENGINE LOCK OUT FEATURE: Some models with auto temp control (ATC) incorporate a feature involving the body control module that prevents blower motor operation when engine coolant temp is below approx (98F) degrees. This feature is cancelled if manual blower motor fan speed is selected.
3. CIRCUIT WIRING AND CONNECTORS: Check all related circuit wiring / connectors / power feed and ground connections. Check for poor pin connections and chafed wiring harness (rub through) causing short to power or ground. Check blower motor control switch (fan switch) operation. Check blower motor relay.
4. INSTRUMENT PANEL SIDE BOLTS: Some models use the large bolts at each end of the instrument / dash panel to provide ground path to the chassis. Check for secure and clean connection at instrument panel side bolts.
5. POWER MODULE: Some models equipped with auto temp control (ATC) use a power module to engage the blower motor relay. Check ATC power module operation. Replace ATC power module as required. IMPORTANT Verify correct wiring harness and resistor card is used for proper blower motor operation.
6. IGNITION SWITCH: Some models use the ignition switch to engage the blower motor relay. Defective ignition switch may allow the blower motor to operate with the ignition off. Check ignition switch operation and related circuit wiring to blower motor relay.
7. BLOWER MOTOR RESISTOR: Disconnect and isolate the battery negative cable and unplug the wire harness connector from the blower motor resistor. Check for continuity between each of the blower motor switch input terminals of the resistor and the resistor output terminal. In each case there should be continuity. If OK, repair the wire harness circuits between the blower motor switch and the blower motor resistor or blower motor as required. If not OK, replace the faulty blower motor resistor.
The blower motor circuit resistor will disengage the power feed to the blower motor if high circuit load is detected. A blown resistor may indicate interference or drag is being placed on the blower motor fan or the blower motor has an internal problem. Blower motor may operate on one speed only if resistor is blown on some models. Suggest blower motor amperage draw test. Amp draw should be approx (13-17) amp when blower is operating on high mode. Check all related circuit wiring and replace blower motor if higher than normal amperage draw is detected.
8. BLOWER MOTOR FAN: Check blower motor fan (squirrel cage) for debris or damage. Verify fan is secure to blower motor shaft.
9. BLOWER MOTOR: Check blower motor operation manually with jumper test wires to power source and ground. Replace blower motor if internal problem is suspected.
10. BLOWER MOTOR SWITCH: Check for battery voltage at the fuse in the Power Distribution Center (PDC). If OK, go to Step 2. If not OK, repair the shorted circuit or component as required and replace the faulty fuse.
(step 2) Turn the ignition switch to the Off position. Disconnect and isolate the battery negative cable. Remove the a/c heater control from the instrument panel. Check for continuity between the ground circuit cavity of the a/c heater control wire harness connector and a good ground. There should be continuity. If OK, go to Step 3. If not OK, repair the open circuit to ground as required.
(step 3) With the a/c heater control wire harness connector unplugged, place the a/c heater mode control switch knob in any position except the Off position. Check for continuity between the ground circuit terminal and each of the blower motor driver circuit terminals of the a/c heater control as you move the blower motor switch knob to each of the four speed positions. There should be continuity at each driver circuit terminal in only one blower motor switch speed position. If OK, test and repair the blower driver circuits between the a/c heater control connector and the blower motor resistor as required. If not OK, replace the faulty a/c heater control unit.