Originally Posted by GParkins
A loose connection can also be described as "resistive." The same applies to a corroded or dirty connection. At the connection point, the increased resistance causes the temperature at the connection to increase. The load of the circuit (in Watts), whether it is a headlight, horn, or fan, remains the same, as does the voltage (14.2). Therefore, if the total circuit resistance goes up, the total circuit amperage decreases proportionally, failing to trip a magnetic breaker. That's why electric motors often have a thermal protection breaker built in. In a locked rotor condition, resistance skyrockets and the current goes down...but the load remains, so the heat increases, sometimes to the point of combustion.

Furthermore, as the conductor heat increases, its resistance drops, exacerbating the problem. I've attached a photo of a resistive connection nearing the end state:

[Linked Image]


Which is why you do thermal testing on control panels in factories. Very scary to see that nut red hot.

JohnV6
2022 CX Plus Four
2025 MG ZS EV aka Trigger