Repair ventilator / habitacle ventilator no longer working

The testing procedure is fairly long ,to much to post here . The first test would be to hook up a factory or some other professional type scan tool an check for DTC'S - diagnostic trouble codes .
Auxiliary HVAC Control Module
The auxiliary HVAC control module is a class 2 device that interfaces between the rear seat occupants and the auxiliary HVAC system to maintain auxiliary air temperature and auxiliary air distribution settings. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, all auxiliary HVAC DTCs and settings will be erased from KAM. The auxiliary HVAC control module will perform a recalibration of the electric actuators when commanded with a scan tool or if KAM is lost. This will ensure the actuators are moving with in the calibrated range. During this calibration process the auxiliary blower motor will be disabled for up to 3 minutes.

Do you know what class 2 is ? It is a serial data network for the control modules to talk to each other .

Air Distribution - Auxiliary Control
The auxiliary HVAC system provides ventilation for the rear seat occupants.
The auxiliary mode actuator shares a control circuit with the auxiliary air temperature actuator. The auxiliary mode is controlled by a rotary knob on the auxiliary HVAC control module. If change of position is required for both actuators, then the auxiliary HVAC control module positions the auxiliary air temperature actuator first. All control circuits for the auxiliary actuators are at a low voltage potential until a change of position is required. The module then applies a high voltage potential to the appropriate control circuit, which will rotate the actuator.

Air Speed - Auxiliary
There are two separate controls for the auxiliary HVAC system. There is the front auxiliary blower motor switch and the auxiliary HVAC control module. If the front auxiliary blower motor switch is in any other position than OFF or REAR, then the auxiliary air temperature actuator mimics the set passenger temperature. The auxiliary mode will mimic the primary mode. If the front auxiliary blower motor switch is in the REAR position, then the system will only function with inputs to the auxiliary HVAC control module. If the front auxiliary blower motor switch is in the OFF position, then the auxiliary HVAC control module does not respond to input. The auxiliary HVAC control module can not request A/C operation from the PCM. The rotary blower switch on the auxiliary HVAC control module provides the operator the ability to select several blower speeds. The auxiliary HVAC control module provides a pulse width modulated (PWM) signal to the auxiliary blower motor through the auxiliary blower motor speed control circuit. The auxiliary blower motor changes speed based on the received PWM signal from the auxiliary HVAC control module. Power and ground are provided to the auxiliary blower motor through the battery positive voltage and ground circuits. Power and ground are provided to the auxiliary HVAC control module by the ignition 3 voltage and the ground circuits.

Auxiliary Console Mode Actuator
The auxiliary console mode actuator is a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5 volt reference, position signal, and two control circuits enable the actuator to operate. The control circuits use either a 0 or 12 volt value to co-ordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the auxiliary HVAC control module grounds one of the control circuits while providing the other with 12 volts. The control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts.
The auxiliary HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, one of the control circuits is grounded. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module grounds both control circuits.

Auxiliary Mode Actuator
The auxiliary mode actuator is a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5 volt reference, position signal, and two control circuits enable the actuator to operate. The control circuits use either a 0 or 12 volt value to co-ordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the auxiliary HVAC control module grounds one of the control circuits while providing the other with 12 volts. The control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts.
The auxiliary HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, one of the control circuits is grounded. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module grounds both control circuits.

It's nice to know how thing's work before trying to fix it .

temp. blend door actuator is probably bad .
Air Temperature Actuator
The air temperature actuator is a 3 wire bi-directional electric motor. Ignition 3 voltage, ground and control circuits enable the actuator to operate. The control circuit uses a 0-12 volt linear-ramped signal to command the actuator movement. The 0 and 12 volt control values represent the opposite limits of the actuator range of motion. The values in between 0 and 12 volts correspond to the positions between the limits.
When the HVAC control assembly sets a commanded, or targeted, value, the control signal is set to a value between 0-12 volts. The actuator shaft rotates until the commanded position is reached. The module will maintain the control value until a new commanded value is needed.

HVAC Control Assembly
The HVAC control assembly is a non-class 2 device that interfaces between the operator and the HVAC system to maintain air temperature and settings. The battery positive and ignition 3 voltage circuits provide power to the control assembly. Two integrated potentiometers control air temperature door position and blower motor speed. The integrated vacuum system controls the mode door position. The control assembly supports the following features:

Fuse for rear air ????? No air coming from rear vent's ? That would be caused by the HVAC blower motor not working . Probably not a fuse issue , if the fuse is blown you have a bigger issue . Fuse's don't just blow for no reason - electrical short circuit, too much current draw etc.. . More then likely it's a problem with the blower motor control module or the blower motor . Located behind the right rear trim panel . But go ahead an check the fuse anyway , fuse # 26 - 25 amp located in the underhood fuse / relay box . marked RR -BLWR/ 110 VAC
Auxiliary Air Speed
The auxiliary blower motor is controlled by the front auxiliary blower motor switch. If the vehicle is equipped with rear DVD (U32), the auxiliary blower motor can be controlled by the overhead console, vehicle entertainment system (VES). The front auxiliary blower switch must be in the AUX position in order to control blower speed from the VES. The VES will send a class 2 message to the HVAC control module requesting a blower motor speed.
The auxiliary blower motor control module is an interface between the HVAC control module and the auxiliary blower motor. The auxiliary blower motor speed control, auxiliary blower motor speed signal, blower motor speed control, and ground circuits enable the control processor to operate. The HVAC control module sends the commanded blower motor speed to the control processor through a 0 to 8-volt linear ramped blower motor speed control circuit. As the blower motor speed control voltage increases, the blower motor speed increases. The control processor sends the actual blower speed to the HVAC control module through a 0 to 12-volt blower motor speed signal circuit. The control processor uses the blower motor ground as a low side control to adjust the blower motor speed. The underhood fuse block supplies 12 volts to the blower motor through the blower motor voltage supply circuit.

Which system ?
HVAC Systems - Manual HVAC Systems - Automatic
If automatic it's probably the blower motor control processor .
Blower Motor Control Processor The blower motor control processor is an interface between the HVAC control module and the blower motor. The blower motor speed control, Blower motor speed signal, battery positive voltage and ground circuits enable the control processor to operate. The HVAC control module sends the commanded blower motor speed to the control processor through a 0 to 12-volt linear ramped blower motor speed control circuit. As the blower motor speed control voltage increases, the blower motor speed increases. The control processor sends the actual blower speed to the control module through a 0 to 12-volt blower motor speed signal circuit. The processor supplies 12volts to the blower motor through the blower motor voltage supply circuit. The control processor uses the blower motor ground as a low side control to adjust the blower motor speed.

That is more then likely a blend or a mode door actuator , they have plastic gears inside that strip an get stuck an then they just click .
The air temperature actuator is a 2-wire bi-directional electric motor. Two control circuits enable the actuator to operate. The control circuits use either a 0-volt or 12-volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds the appropriate control circuit for the commanded direction. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction.
The mode/recirculation actuator is a 2 wire bi-directional electric motor. Two control circuits enable the actuator to operate. The control circuits use either a 0 or 12-volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds the appropriate control circuit for the commanded direction. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction.
The HVAC control module determines the door position by counting motor pulses on one of the control circuits. These pulses are small voltage fluctuations that occur when the brush is shorted across 2 commutator contacts as the motor rotates. As the actuator shaft rotates, the HVAC control module monitors the voltage drop across an internal resistance to detect the pulses. The HVAC control module converts the pulses to counts with a range of 0-255 counts. The HVAC control module uses a range of 0-255 counts to index the actuator position.
Your have to figure out which side of the heater box the noise is coming from . The Temperature Valve Actuator Replacement - Right Side - the glove box needs to come out to get to it .
Temperature Valve Actuator Replacement - Left Side
the driver side knee bolster needs to be removed