Open Circuit

An open circuit is a break in the electrical path that stops current from flowing completely. Think of it like a garden hose with a complete cut — no water flows at all regardless of pressure. The component receives no power, no ground, or no signal and simply does not operate. Unlike a short to ground, an open circuit does not blow fuses. The circuit is just interrupted somewhere.

Use a voltmeter and trace through the circuit from the power source toward the load. At some point voltage will be present on one side of a connection and absent on the other side. That is the open — right there between those two test points. Narrow it down section by section until you find the exact location.

Corrosion inside connector pins that looks perfectly clean from the outside. You can have a terminal that looks shiny and fine but when you probe inside the cavity the corrosion has eaten through the contact surface and there is no connection. Broken wires inside intact insulation — the copper conductor cracked and separated but the plastic jacket held its shape, making the wire look completely undamaged externally. This is especially common in door harnesses that flex regularly. Always back-probe connectors with a proper back-probe pin — forcing a test lead into a connector spreads the terminal and creates a new open right where you are trying to diagnose one.