The aux fan should kick on when the air conditioning is turned on. The aux fan should also run a self test when the engine is first started so it runs for a short time then. You may have a clutch fan going bad. If the fan turns easily by hand when the engine is at operating temp it is an indication the clutch fan is dying. Now that the cluster is unlocked you can monitor temp easier and verify the gauge is accurate. The normal thermostat controlled operating temp is 225 degrees. That is not necessarily the optimum performance temp but what is needed to be in compliance with emission standards. Sometimes when an engine is marginally overheating you can smell coolant that is forced out at the weakest link (should be the cap) but it is a small amount that is not visually evident an takes a long time before it is obvious the coolant level is low. Before replacing the aux fan be sure the temp sensor is working. The fan can be fine, just not getting the message to get to work.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas