Service function guideRadiator Fan Diagnosis

This radiator fan diagnosis guide gives working mechanics and serious DIY owners a complete, repeatable method for testing fan motors, relays, and control modules across a wide range of vehicles. It explains how the cooling fan circuit is designed to operate, when a no-run or always-on complaint justifies a full electrical diagnosis, and how to prepare the vehicle and test equipment before any probing begins. The step-by-step procedure covers commandeering the fan with a scan tool, verifying powers and grounds, bench testing the motor, and isolating a failed relay or module, so the reader can confidently condemn the correct component instead of guessing. After finishing, the reader will be able to confirm a repair with a commanded and temperature-driven fan run and hand the vehicle back with the cooling system verified.