Fighting a fire that's raging through a forest requires the strength and bravery of more than one man. Similarly, cooling down your engine requires more than just having a radiator. You need an electric cooling fan to help maintain the engine coolant's temperature as it passes through the radiator. You also need your Mercedes-Benz S430 radiator fan to help your air conditioning in keeping the cabin cool. A faulty fan can cause both your radiator and your engine to overheat. That's why you need to know how to immediately diagnose any issues with your radiator fan.
Your Mercedes-Benz S430 radiator fan is engineered to start up whenever you've got the air conditioning on, even if your engine isn't hot. That's why you can start your engine and turn your air conditioning all the way to its highest setting in order to determine the health of your fan. If your fan runs, then its motor, relay, fuse, and wiring are all working well. If it doesn't come on, or if the air inside your car isn't as cold as it should be, then you've got a faulty fan on your hands.
As an electrical component of a car, one of the first things that you should check when your radiator fan malfunctions is it's fuse. Locate the correct fuse box and pull out the radiator's fuse to inspect it. If the fuse is no longer intact, replace it with a new one.
If the fuse is in good condition, then you'll need to check the fan's wires. Unplug both the positive and negative wires and check them with a voltmeter. If they don't put out 12 volts of direct current then you'll need to have them replaced.
If the wires are also fine, then you'll need to check the fan relay. If the voltmeter shows that there's a current running through the fan, then you need to replace the fan itself.
If both your fan and its circuit seems fine, then the problem may lie with the fan clutch. This part connects your Mercedes-Benz S430 radiator fan with your engine. Over the years, the fan clutch can burn out or its springs can corrode. If you see that the clutch is too damaged, replace it immediately.