Charge Temperature & Coolant Switch

Turn ignition off and disconnect wire from charge temperature switch. Connect 1 lead of ohmmeter to good engine ground (or to switch's ground terminal). Connect other lead to center terminal of coolant switch. Check for continuity.
On a cold engine, continuity should be present (resistance less than 100 ohms). If not, replace switch. The charge temperature switch must be cooler than 60°F to obtain this reading. On an engine at normal operating temperature, the terminal should show no continuity. If it does, replace coolant switch.