A tool to measure resistance of a wire harness is disclosed herein. An example disclosed tool includes a connector with first and second plugs. The example disclosed tool also includes a resistor. A first terminal of the resistor is electrically coupled to the first plug. Additionally, the example disclosed tool includes a thermal switch attached to the resistor with a thermally conductive adhesive. A first terminal of the thermal switch is electrically coupled to a second terminal of the resistor, and a second terminal of the thermal switch is electrically coupled to the second plug.