Seat Heaters System Description
Control/Function
The front seat heater control unit sets the seat heater to High/Mid/Low or OFF based on the seat heater switch signals received from the climate control unit via B-CAN. The front seat heater control unit monitors the thermistor resistance, the voltage/current/temperature to the heater, and the presence of communication with the climate control unit. Also, the system stores DTCs when a malfunction is detected in the front seat heater control unit.
Automatic Operation
Based on the outside air temperature, A/C target temperature and other factors, the climate control unit calculates the optimal front seat heater setting. The climate control unit sends this setting request to the front seat heater control unit via B-CAN. When operating in auto mode or during remote engine start, the front seat heater control unit will operate per B-CAN setting request from the climate control unit.
Thermistor and Breaker
The seat cushion heater has a thermistor and breaker. The thermistor and breaker protect the seat heater circuit from overheating. The value of the thermistor is inputted to the control unit.
The seat heater temperature is controlled by breaker ON and OFF condition.
| ON | OFF | |
|---|---|---|
| Breaker | 95 - 113 deg.F (35 - 45 deg.C) | 115 - 129 deg.F (46 - 54 deg.C) |
Failsafe Function
Thermistor Circuit Open Failure
Thermistor circuit open refers to a condition in which the value of the thermistor built in the seat cushion heater continues to be higher than the threshold value for a few seconds. When the control unit detects a shift from the normal operation condition to this condition, it stops the seat heater operation and turns off the seat heater switch indicators.
Thermistor Circuit Short Failure
Thermistor circuit short refers to a condition in which the value of the thermistor built in the seat cushion heater continues to be lower than the threshold value for a few seconds. When the control unit detects a shift from the normal operation condition to this condition, it stops the seat heater operation and turns off the seat heater switch indicators.
Heater Circuit Current Error
When the control unit detects an abnormal current value in the heater circuit, it stops the heater output immediately after detection and turns off the seat heater switch indicators.