Operating Modes
All available operating modes for C61 and C67 are listed below. The actual operating modes on your system will vary by model and will not have all modes listed.Off
The blower motor and A/C compressor are turned OFF.
Vacuum is not applied to any of the vacuum actuators; the air inlet valve is in the outside air position; the heater-A/C-bi-level valve vacuum actuator is in the bi-level position and the defrost-A/C valve vacuum actuator is in the defrost position.
When the vehicle is moving, air flowing over the vehicle increases air pressure just ahead of the windshield, so some air is forced into the air inlet, through the HVAC module and out the defroster ducts and floor outlets.
Temperature control circuitry is still activated so the air forced through the system can be directed through the heater core and warmed, if desired.
Max A/C
Blower motor circuitry is turned ON and blower speed can be adjusted using the fan speed knob. The A/C compressor is activated and runs to keep the evaporator core at about 1°C (33°F).
Vacuum is applied to the air inlet vacuum actuator, the defrost-A/C valve vacuum actuator and one side of the heater-A/C-hi-level valve vacuum actuator; the air inlet valve is in the recirc position; the defrost-A/C valve is in the A/C position and the heater-A/C-bi-level valve is in the A/C position.
Interior air is pulled into the system by the blower, the air is cooled and dehumidified, then heated as necessary, and forced out the instrument panel outlets.
Temperature control circuitry is activated so the temperature knob can be used to adjust discharge air temperature.
Norm A/C
Blower motor circuitry is turned on and blower speed can be adjusted using the fan speed knob. The A/C compressor is activated, and runs to keep the evaporator core at about 1°F (33°F).
Vacuum is applied to the defrost A/C valve vacuum actuator and one side of the heater-A/C-bi-level valve vacuum actuator; the air inlet valve is in the outside air position; the defrost-A/C valve is in the A/C position and the heater-A/C-bi-level valve is in the A/C position.
Outside air is pulled into the system by the blower, the air is cooled and dehumidified, then heated as necessary, and forced out the instrument panel outlets.
Temperature control circuitry is activated so the temperature knob can be used to adjust discharge air temperature.
Bi-Level
Blower motor circuitry is turned on and blower speed can be adjusted using the fan speed knob. The A/C compressor is activated and runs to keep the evaporator core at about 1°C (33°F).
Vacuum is applied to the defrost A/C valve vacuum actuator; the air inlet valve is in the outside air position; the defrost-A/C valve is in the A/C position and the heater-A/C-bi-level valve is in the bi-level position.
Outside air is pulled into the system by the blower, the air is cooled and dehumidified, then heated as necessary, and forced out the instrument panel and floor outlets.
Temperature control circuitry is activated so the temperature knob can be used to adjust discharge air temperature.
Vent
Blower motor circuitry is turned on and blower speed can be adjusted using the fan speed knob.
Vacuum is applied to the defrost-A/C valve vacuum actuator and one side of the heater-A/C-bi-level valve vacuum actuator; the air inlet valve is in the outside air position; the defrost-A/C valve is in the A/C position and the heater-A/C-bi-level is in the A/C position.
Outside air is pulled into the system by the blower and forced out the instrument panel outlets.
Temperature control circuitry is activated so the air flowing through the system can be directed through the heater core and warmed, if desired.
Heater
Blower motor circuitry is turned on and blower speed can be adjusted using the fan speed knob.
Vacuum is applied to one side of the heater-A/C-bi-level valve vacuum actuator; the air inlet valve is in the outside air position; the defrost-A/C valve is in the defrost position and the heater-A/C-bi-level valve is in the heater position.
Outside air is pulled into the system by the blower and forced out the floor outlets.
Temperature control circuitry is activated so the air flowing through the system can be directed through the heater core and warmed, if desired.
Defog
Blower motor circuitry is turned on and blower speed can be adjusted using the fan speed knob. The A/C compressor is activated and runs to keep the evaporator core at about 1°C (33°F).
Vacuum is not applied to any of the vacuum actuators; the air inlet valve is in the outside air position; the heater-A/C-hi-level valve vacuum actuator is in the bi-level position and the defrost-A/C valve vacuum actuator is in the defrost position.
Outside air is pulled into the system by the blower, the air is cooled and dehumidified, then heated as necessary, and forced out the windshield defroster and floor outlets.
Temperature control circuitry is activated so the temperature knob can be used to adjust discharge air temperature.
Defrost
Blower motor circuitry is turned on and blower speed can be adjusted using the fan speed knob. The A/C compressor is activated and runs to keep the evaporator core at about 1°C (33°F).
Vacuum is applied to one side of the heater-A/C-bi-level valve vacuum actuator, the air inlet valve is in the outside air position; the defrost-A/C valve is in the defrost position and the heater-A/C-bi-level valve is in the A/C position.
Outside air is pulled into the system by the blower, the air is cooled and dehumidified, then heated as necessary, and forced out the windshield defroster outlets.
Temperature control circuitry is activated so the temperature knob can be used to adjust discharge air temperature.
Recirc
When vacuum is applied to the air inlet vacuum actuator, and the defrost-A/C valve and one side of the heater-A/C-hi-level valve vacuum actuator, the air inlet valve is moved to the recirc position.
Interior air is pulled into the system by the blower, if A/C is selected the air is cooled and dehumidified, then heated as necessary, and forced out the instrument panel outlets.
Temperature control circuitry is activated so the temperature knob or level can be used to adjust discharge air temperature.
Upper
When vacuum is applied to the defrost A/C valve vacuum actuator and one side of the heater-A/C-BI-Level valve and the air inlet valve is in the outside air position. The defrost-A/C valve and the heater-A/C-BI-Level valve are in the A/C position.
Outside air is pulled into the system by the blower. If A/C is selected, the air is cooled and dehumidified, then heated as necessary, and forced out the instrument panel outlets.
Temperature control circuitry is activated so the temperature knob or level can be used to adjust discharge air temperature.
Lower
When vacuum is applied to the defrost A/C valve actuator only. All of the other actuators are venting. The air inlet valve is in the outside air position.
Outside air is pulled into the system by the blower. If A/C is selected, the air is cooled and dehumidified, then heated as necessary, and forced out the instrument panel outlets.
Temperature control circuitry is activated so the temperature knob or level can be used to adjust discharge air temperature.
Rear Defogger and Heated Mirrors
With the ignition switch in RUN, voltage is applied to the heater and A/C control. When the rear defogger control switch is pressed, a momentary enable signal is provided for the timer-relay. The timer-relay contracts close, lighting the system ON LED and powering the rear defogger and heater mirror(s) (if equipped). The rear window and outside mirrors become warm to remove condensation from the glass surfaces.
The first time the rear defogger switch is pressed, the solid state timer allows the rear defogger and heated mirror(s) to operate for approximately 10 minutes. Each time the rear defogger switch is pressed thereafter, the solid state timer resets to operate for 5 minutes when the ignition switch is turned OFF, then back to RUN. The timer also shuts off when the rear defogger control switch is pressed while the rear defogger and heated mirror(s) are already on.