Variable Resistors

Three types of variable resistors are used: rheostats, potentiometers, and thermistors.

• RHEOSTAT - Toyota uses a rheostat on the headlamp switch to dim or brighten dash panel lighting. Rheostats have two connections ... one to the fixed end of a resistor, one to a sliding contact on the resistor. Turning the control moves the sliding contact away from or toward the fixed end, increasing or decreasing the resistance.

• POTENTIOMETER - Toyota uses a potentiometer in the EFI airflow meter. Potentiometers have three connections ... one at each end of a resistor and one on a sliding contact. Turning the control places more or less resistance in the circuit.

• THERMISTOR - Toyota uses NTC (negative temperature coefficient) thermistors in temperature sensors and PTC (positive temperature coefficient) thermistors in the electric assist choke. Both types of thermistors change resistance with increasing temperature (NTC, resistance goes down as temperature goes up; PTC, resistance goes up as temperature go up.)

NTC/PTC THERMISTORS

NTC THERMISTOR

NTC/PTC THERMISTORS

NTC THERMISTOR

-HIGHER

-HIGHER

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Responses

  • vanessa
    Does a 2008 toyota yaris have a rheostat or a potentiometer?
    3 years ago
  • feorie
    What is a variable resistor for in a 3rzfe engine?
    10 months ago
  • GRETCHEN
    What does resistor R834 control on a engine control toyota 896613D070?
    5 months ago

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