The driver and front passenger climate control seat (CCS) systems each consist of the following components:
| • | Heated/cool seat switch |
| • | Seat cushion heated/cool ventilation module |
| • | Seat back heated/cool ventilation module |
| • | Driver door module (DDM) |
| • | Passenger door module (PDM) |
| • | Climate control seat module (CCSM) |
| • | HTDST LF Fuse 10-amp |
| • | HTDST RF Fuse 10-amp |
| • | IGN 3 Fuse 10-amp |
Air Circulation
When the heated/cool seat switch is pressed to initiate operation of the climate control seat (CCS) system, cabin air is drawn through the heated/cool ventilation module air filter, then directed through passages in the foam of the seat cushion and seat back to the seat's occupant. In order for the CCS system to operate to its optimum performance, it is crucial to have unrestricted air flow through the system. A dirty or restricted air filter, the blockage of an exhaust air duct, a misaligned heated/cool ventilation module, or incorrect foam installation of the seat cushion or seat back will all have negative effects on CCS operation.
Heated/Cool Ventilation Module
Each heated/cool seat has 2 ventilation modules, one located under the seat cushion and one located in the seat back. These modules are controlled by the climate control seat module (CCSM). Each ventilation module contains a thermo-electric device (TED), a temperature sensor, and a blower motor. The TED and temperature sensor are mounted downstream of the blower motor. Each TED consists of a circuit of positive and negative connections sandwiched between 2 ceramic plates. Each ceramic plate is equipped with copper fins for heat exchange. The air flowing past these fins is either directed as conditioned air into the seat cushion and seat back, or directed into the cabin as waste air.
A TED is essentially a solid state heat pump that is used to heat or cool the air supply to the seat cushion and seat back. When voltage is applied to a TED, one side releases energy as heat, while the opposite side absorbs energy and gets cold. When the polarity of the current flow to the TEDs is switched, the hot and cool sides of the TED reverse.
During the following climate control seat system description and operation, the TEDs, blower motors, and temperature sensors will be referenced independently even though they are all packaged together as a module.
Climate Control Seat (CCS) System
Both the driver and passenger seats have independent climate control seat (CCS) systems. A climate control seat module (CCSM) mounted below each seat cushion electronically controls each CCS system. The CCSM receives power from both battery positive voltage and ignition 3 voltage. The ignition must be in the ON position in order for the CCS system to operate.
Once a CCS system is activated, cabin air is drawn through the seat blower motors and directed across the fins of each of the thermo-electric device (TED) located under the seat cushion and in the seat back. The air is either heated or cooled as it passes over the TEDs. This conditioned air is then directed through channels in the foam of the seat pad and through small holes in the seat cover to the occupant. Once the system is activated, the CCSM uses a set of algorithms to control the temperature of the selected heating or cooling modes.
Climate Control Seat Module (CCSM) Power and Ground
Battery positive voltage is supplied at all times to each climate control seat module (CCSM) through the battery positive voltage circuit and the HTDST LF fuse and the HTDST RF fuse located in the rear fuse block. This voltage is used by each CCSM to supply power to the thermo-electric devices (TEDs) and the blower motors. Battery positive voltage is also supplied to each CCSM through the ignition 3 voltage circuit and the IGN 3 fuse also located in the rear fuse block. The IGN 3 voltage is used to power up each CCSM and allows the climate control seat (CCS) system to operate only with the ignition in the ON position. Each CCSM is grounded through the module ground circuit to the ground stake.
Modes of Operation
There are 3 modes available for climate control seat (CCS) system operation, heated seat, cool seat, and back only heat operation. When a heat or cool seat temperature signal request is received, the climate control seat module (CCSM) will activate both the seat cushion and seat back ventilation modules. When the seat BACK ONLY mode button is pressed once, the CCSM will deactivate the seat cushion ventilation module and leave the seat back ventilation module ON. Press the BACK ONLY mode button a second time and the CCSM will re-activate the seat cushion ventilation module.
Heated/Cooled Seat Switch and Door Module
The driver and front passenger seats are controlled by a separate heated/cool seat switch. Battery positive voltage is supplied to the heated/cool seat switch by the respective door module. The door module plays an important part of the climate control seat (CCS) operation, first by relaying the selected switch inputs to the climate control seat module (CCSM), and second, by controlling the mode and temperature indicators of the heated/cool seat switch.
The following describes the sequence of operation of the heated/cool seat switch, and how the door module responds to each of the switch inputs.
| • | High Temperature--When either the heat or cool seat switch is pressed once, battery positive voltage is applied through the switch contacts and the switch signal circuit to the door module. In response to this input, the door module then sends a pulse width modulation (PWM) signal through the heated/cool seat mode signal circuit to the CCSM indicating the switch input. The door module then applies a ground through the appropriate heat or cool seat indicator control circuit to the switch, illuminating the selected heat or cool mode indicator. At the same time, the module also applies a ground through the high, medium, and low temperature indicator control circuits of the switch illuminating all 3 temperature indicators, indicating the high temperature mode. |
| • | Medium Temperature--When the switch is pressed a second time, the door module signals the CCSM of the medium temperature request. The door module then removes the ground from the high temperature indicator, leaving the medium and low temperature indicators illuminated, indicating the medium temperature mode. |
| • | Low Temperature--When the switch is pressed a third time, the door module signals the CCSM of the low temperature request. The door module then removes the ground from the medium temperature indicator, leaving the low temperature indicator illuminated, indicating the low temperature mode. |
| • | System Off State--After the switch is pressed a fourth time, the door module signals the CCSM of the system OFF request. The door module then removes the grounds from indicator control circuits turning OFF the appropriate heat or cool mode indicator and the low temperature indicator. |
| • | Seat Back Only Heat Mode--The back only mode will operate only in the heat mode in any one of the above mentioned temperature settings. When the back only switch is pressed once, the door module signals the CCSM of the back only mode request. The door module then supplies a ground through the seat back only mode indicator control circuit to the switch, illuminating the BACK ONLY mode indicator. When the switch is pressed a second time, the door module signals the CCSM to cancel the back only mode. The door module then removes the ground from the indicator control circuit turning OFF the BACK ONLY mode indicator. |
Temperature Sensors
As mentioned above in the heated/cool ventilation module description, the seat cushion and seat back temperature sensors are each packaged with a thermo-electric device (TED) and blower motor as an assembly. The seat temperature sensors are thermistors which are attached directly to the fins of each TED. The climate control seat module (CCSM) supplies a 5-volt reference voltage through the temperature sensor signal circuit and ground through the temperature sensor low reference circuit to the respective seat cushion and seat back temperature sensors. As the temperature of the TED changes, the resistance of the thermistor varies changing the feedback voltage of the temperature sensor signal circuit. This voltage varies from 0.5-4 volts. The CCSM monitors this voltage signal to determine the fin temperature so that it can adjust and maintain the seat temperature to the selected switch input.
°C | °F | OHMS |
|---|---|---|
Temperature vs Resistance Values (Approximate) | ||
60° | 140° | 319.9 |
50° | 122° | 433.1 |
40° | 104° | 596.6 |
30° | 86° | 837.5 |
20° | 68° | 1200 |
10° | 50° | 1757 |
0° | 32° | 2633 |
-10° | 14° | 4047 |
-20° | -4° | 6401 |
-30° | -22° | 10,450 |
-40° | -40° | 17,670 |
Blower Motors
Also, as mentioned above in the heated/cool ventilation module description, the seat cushion and seat back blower motors are each packaged with a thermo-electric device (TED) and temperature sensor as an assembly. Each blower motor contains logic that will allow for the blower to operate only when the ignition is in the ON position. When the ignition is ON and the climate control seat module (CCSM) is powered up, the module supplies battery positive voltage through the blower voltage reference circuits to the logic of the blower motors. When the heated/cool seat switch is pressed, the CCSM applies a pre-determined voltage through the blower speed control circuits to the blower motors. The module also supplies each blower motor with a ground path through the blower low reference circuits.
With the climate control seat (CCS) system, the speed of the blower motor is not related directly to the High, Med, or Low input from the heated/cool seat switch. The speed of the blower motor is related directly to TED temperature as described below in heated and cooled seat operation.
Heated Seat Operation
When the heated seat switch is pressed for High Heat, the Temperature Set Point and the climate control seat module (CCSM) will transition to the HEAT state. In the heat state, the CCSM applies a pre-determined voltage through the ventilation module heat control circuits to the heat side of the thermo-electric devices (TEDs), while providing a ground through the ventilation module cool control circuit to the cool side of the TEDs. A pre-determined voltage is also applied to the blower motors. The CCSM uses the following sequence, beginning with the Heat SoftStart Mode, to achieve the set point temperature before it can enter the Control Heat Mode. If the seat temperature is already above the Temperature Set Point, the CCSM will skip the Heat SoftStart Mode and proceed to the Control Heat Mode.
| • | Heat SoftStart Mode--While transitioning to the heat mode, the CCSM will initiate the SoftStart Mode. The intent of the Heat SoftStart Mode is for the module to bring the ventilation module fin temperature up to the pre-determined Temperature Set Point of the High Heat Mode. The module does this by setting the blower motor speed control voltage to 3 volts while ramping up the ventilation module voltage from 0 volts to the maximum available voltage, at which point, the system transitions to High Heat Mode. |
| • | High Heat Mode--Upon completion of the Heat Soft/Start Mode, the CCSM will initiate High Heat Mode. The intent of the HIGH Heat Mode is to increase the fin temperature to the pre-determined Temperature Set Point in order for the CCSM to go into the Control Heat Mode. The CCSM does this by maintaining the TED at the maximum voltage, while maintaining the minimum required airflow across the fins. After a maximum duration of 3 minutes, or upon achieving the pre-determined Temperature Set Point, the system transitions to the Control Heat Mode. |
| • | Control Heat Mode--At the completion of High Heat Mode, the CCSM will initiate Control Heat Mode. The intent of the Control Heat Mode is to maintain the desired fin temperature or the set point temperature. The CCSM does this by first adjusting the voltage supply to the blower motor to control blower motor speed and second by controlling the voltage supplied to the TED. The CCSM updates these voltages once every second. Increasing the blower motor speed will decrease the fin temperature. If the maximum blower motor speed is achieved and the fin temperature is still above the set point of high heat, the CCSM will then begin to control the TED voltage to achieve Temperature Set Point. Decreasing the TED voltage decreases the fin temperature. |
| If the CCSM is trying to raise the fin temperature to set point by using TED voltage, and the fin temperature cannot be raised because the TED voltage is at the maximum, the CCSM reduces the blower motor speed to achieve the Temperature Set Point. |
Cooled Seat Operation
When the cool seat switch is pressed for High Cool, the climate control seat module (CCSM) will transition to the COOL state. In response to this command, the CCSM applies a pre-determined voltage through the ventilation module cool control circuits to the cool side of the thermo-electric devices (TEDs) while providing a ground through the ventilation module heat control circuits to the heat side of the TEDs. A pre-determined voltage is also applied to the blower motors. The CCSM uses the following sequence, beginning with the Cool SoftStart Mode, to achieve the set point temperature before it can enter the Control Cool Mode.
| • | Cool SoftStart Mode--The intent of the Cool SoftStart Mode is for the CCSM to bring the TED fin temperature to the pre-determined Temperature Set Point of the High Cool Mode. The CCSM does this by setting the blower motor speed control voltage to 0 volts, while ramping up the TED voltage from 0 volts to maximum voltage for 10 seconds. Then, with the TEDs at maximum voltage, the CCSM will increase the blower speed to maximum voltage for 1 minute, at which point the system transitions to High Cool Mode. |
| If the cool seat switch was initially set to LOW or MED COOL, at this point, the system would by-pass the High Cool Mode and transition directly to the Control Cool Mode. |
| • | High Cool Mode--The intent of the HIGH Cool Mode is for the fin temperature to reach the pre-determined Temperature Set Point of the Control Cool Mode. The CCSM does this by initially setting the blower speed voltage to 4.5 volts, then ramping the voltage to the maximum available voltage for 1 minute. After 1 minute, it sets the blower voltage to 10.5 volts, while maintaining the TED voltage at 8.7 volts. Then it remains at these conditions for 3 minutes, after which the system will transfer to the Control Cool Mode. |
| • | Control Cool Mode--At the completion of High Cool Mode, the CCSM will initiate Control Cool Mode. The intent of the control cool mode is to maintain the set point fin temperature, first by adjusting the speed of the blower motor, by controlling the voltage supplied to the motor, and second, by controlling the TED voltage. The CCSM updates these voltages once every second. |
