One of three things. 1. The Switch is broken 2. the Window motor is not working 3. A broken wiring.
Trouble shooting the switch is simplest. Take a know working switch and simply plug in and test. if it fixes the problem that's it. (You may try putting the only switch back in just in case it was a loose sensor)
The motor can be tested by applying 12V to the motor and see if it works? if not replace!
It the motor works with 12v applied look for a broken wire.
You have bad window switches. Remove and carefully disaasemble and clean the contacts of the switches. also you need to make sure fuse is in good shape. if its not the fuse,or switch, it might be the regulator is broken, is usually the case.
fuel gauge not working and power windows and radio.2004 mercury mountaineer.
The convenience relay that is located in the trunk of a Mercedes C280 may need to be replaced if the power seats are not working. Bad or loose wiring can be another cause for power seats to stop working.
the motor for your power windows is shot, or your wiring is gone
If all the windows quit working you need to look for a blown fuse in the fusebox.
In the trunk on your right hand side.
Probably
Check the fuse.
Blown fuse.
You might want to get out your owners manual and see which fuse controls the windows and make sure it is not a fuse. Since you didn't mention the make of the car I have no more advice other than the fuse.
you may want to check the fuses, the fuse box on this car is loacted under the hood on the right side in the back. There shouldn't be any other reason for it to stop working. Hope this helps.
Could be a fuse if both stopped working. or a wire ,both windows are hooked up to same wire.