Toyota Yaris: Heated Steering Wheel System / System Description

SYSTEM DESCRIPTION

HEATED STEERING WHEEL SYSTEM

(a) The steering heater warms up the steering wheel when the steering heater switch is turned on.

(b) The steering heater uses a control thermostat inside the steering wheel to maintain the steering wheel at the specified temperature.

OPERATION DESCRIPTION

(a) When the steering heater switch is turned on with the ignition switch ON, the heater indicator light illuminates and the heater inside the steering wheel operates. If the steering heater switch is pushed again, the heater indicator light turns off and the heater stops operating.

(b) A control thermostat and an additional thermostat used as a safety device to prevent overheating are installed inside the steering wheel.

CONTROL DESCRIPTION

(a) When the steering heater switch is turned on, current flows to the LO and HI sides, starting the warming operation to warm the steering wheel.

(b) When the temperature of the steering wheel reaches the operation temperature of the control thermostat, the control thermostat stops the flow of current to the HI side, only allowing current to flow to the LO side and thereby maintaining the temperature of the steering wheel.

(c) While operating to maintain the temperature of the steering wheel, if the temperature drops to the operation temperature of the control thermostat, the control thermostat restarts the flow of current to both the LO and HI sides to warm the steering wheel.

(d) While the steering heater switch is on, the control thermostat automatically stops and restarts the flow of current to the HI side according to the temperature of the steering wheel, continuously maintaining the specified temperature.

(e) If a malfunction occurs in the steering heater circuit and the temperature exceeds the specified temperature, the overheating prevention thermostat stops the flow of current to the circuit, the heater indicator light turns off and the heater stops operating.