* High Current Draw: The starter motor requires a massive amount of current (often hundreds of amps) to turn the engine over. This is a significant electrical load.
* Resistance in the Wiring: Even though starter wires are thick (low gauge) to handle this current, they still possess some electrical resistance. According to Ohm's Law (V = IR), any resistance in a circuit with a high current (I) will cause a voltage drop (V) across that resistance. This voltage drop manifests as heat due to resistive losses (power dissipated as heat = I²R).
* Poor Connections: If the connections at the battery terminals, the starter motor terminals, or anywhere along the starter cable are corroded, loose, or otherwise have high contact resistance, this concentrates the heat generation in that small area, making it even hotter. A poor connection acts like a resistor in series, dramatically increasing resistance and heat.
* Small Wire Gauge: If, for any reason, the wire gauge is thinner than what's specified for the vehicle, the resistance will be higher and more heat will be generated.
* Length of the Wire: A longer starter cable will inherently have more resistance than a shorter one. This is why it's important to maintain the original length as much as possible when replacing it.
In essence, the heat is a byproduct of the significant energy required to turn the engine over, and the unavoidable resistance within the electrical circuit. Excessive heat is a sign of a problem, usually related to high resistance in the circuit. A hot starter wire should not be ignored, as it indicates a potential problem that could lead to wire failure, fire hazard, or damage to the starter motor.
