Control Current

Other components and systems use resistance for current control. Ignition primary resistors, also called ballast resistors, maintain and protect the electronic control unit (ECU) from excessive current. The headlamp rheostat adds or subtracts resistance to dim or brighten interior lamps. A carbon pile resistance in the Sun VAT-40 tester "loads" the battery for cranking-voltage and charging system tests. A sliding contact resistance is used on some A/C and heating controls to adjust interior temperature by increasing or decreasing air volume and fan speed. A wire-wound resistor is used on some fuel pumps to reduce pump speed.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

Don't pay hundreds of dollars to find out what is wrong with your car. This book is dedicated to helping the do it yourself home and independent technician understand and use OBD-II technology to diagnose and repair their own vehicles.

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