That simple observation proves the high-current part of the circuit, including the fan motor, is working. Be aware a lot of GM vehicles have to get hotter than 225 degrees before the fan turns on. Are you having an overheating problem?
To test the entire system, unplug the two-wire coolant temperature sensor while the ignition switch is on. Most systems will turn the fan on by default in case the engine runs hot and the engine computer does not know it. If that makes the fan run, the system is working.
You can also watch the coolant temperature on a scanner to see what the computer is seeing and responding to. The scanner will also let you do an actuator test and run the fan without having to run the engine or get it hot.
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Monday, January 29th, 2018 AT 2:47 PM
