Diagnosing a Faulty Mercedes Benz 420SEL Window Switch
The window switch is one of the most convenient components in any vehicle because it allows you to lower or raise the glass windows with just the use of your fingertip. However, it's quite inevitable even for this little guy to become faulty in a matter of time. To avoid having troubles with controlling the windows of your car, here are some troubleshooting tips to help you diagnose if it's broken.
Push the window switch to lower the glass window. If it doesn't go down, but you hear humming sounds, then there's a problem with the gears or the motor. Replacing these would entail you to take out the door panel so that you can see which one is not working. Use a test light to check if the motor has power and if the window gears have broken teeth.
Since you've already taken out the door panel when you checked the motor and the gears, you might as well check up on the regulator. Take a good look at the window regulator, which secures the window to the frame. If it's worn, it won't be able to work the way it should. You'll have to replace this part in order to easily control the windows using the Mercedes Benz 420SEL window switch.
Using a test light, inspect the main circuit relay to check if there's voltage coming from it. If there's voltage, there's a short in the wire that's coming from the main wire, which provides power to the switches. If there's none at all, then inspect the main wire to know if there's voltage in the relay switch. If that's the case, then you must have the wire replaced. Otherwise, the problem with the window switch is caused by a short in the wire from the fuse to the relay.
With your key in the ignition, turn it to on and lower all the windows on your vehicle. If none of them is working, then the problem is caused by a worn fuse. Look for the fuse box and check if the fuse is blown. Replace it with a new one so that you can still operate the glass windows on your ride.