Starting & Charging System Relays, Sensors, Cables

The battery, alternator, and starter may be the stars of the starting & charging system, but they would be useless without the relays, wiring and connectors that complete the system and conduct the current necessary for operation. And quite often it’s a bad starter relay, frayed or broken wire, or corroded connector that’s the cause of a dead battery or no-start, not a main component. But major or minor, we have the parts to get your vehicle functioning again.

The starter relay allows low current and lighter gauge wire to control the high current needed to operate the starter motor, avoiding the danger and complexity of routing high current carrying, heavy gauge wire to the ignition switch. The battery cables and all the wiring and connectors in the starting & charging system must be of the proper gauge, and the integrity of the wire and condition of the terminals must be sufficient to conduct the required current.

The starter relay is part of the starter control circuit. It can be controlled by the ignition switch or through the Powertrain Control Module (PCM). In an ignition switch controlled relay, when the switch is turned to the START position, current is applied to the relay coil, creating a magnetic field that closes the power circuit contacts and sends voltage to the starter solenoid. Controlling the relay with the PCM allows anti-theft overrides to be employed if the wrong ignition key is used. If the starter relay is suspected as the cause for a no-start, voltage tests can be used to determine relay condition.

Due to the large current demands of the starter motor, the battery cables are the heaviest gauge wires in a vehicle’s electrical system, typically ranging from 6 to 4/0 gauge. They are constructed from stranded copper wire encased in an insulated covering. The positive battery cable is connected to the positive battery terminal and starter solenoid. The negative cable is connected to the negative terminal and the chassis or engine block. A cable that is cut or frayed will have high resistance and may not be able to conduct the current needed to start the engine. The location of high resistance can be found with a voltage drop test.

Corrosion and damaged terminals are another cause of excessive circuit resistance. While battery cable terminals can often be cleaned, it is usually difficult or impossible to clean and repair the small, delicate contacts in alternator, voltage regulator, and other electrical connectors in the starting & charging system. We offer original equipment style replacement connectors complete with wires, commonly known as “pigtails”, which can easily be spliced into the harness. Our battery cables and starter relays are also configured for direct fit, and we carry other system needs like battery sensors and terminal protectors.