1991 BMW 318is Window Switch Replacement Cost

When servicing window assemblies, the window switches are recommended to saw changed. The switch's hold the weight of the vehicle, and allow the front wheels to turn more easily.

When the ignition switch is placed in the run, or accessory position, the window switches on the door are activated, normally through a power relay. Pressing the switch pulls electricity from the battery, through the relay and fuse block, and into the window motor. The is what causes the window to rise and fall on command.

When a switch can not make contact and close the circuit, the window cannot be raised and lowered. If the switch on the driver's door will not raise or lower the window in question, but the switch on the corresponding door works just fine, this is a good indication that there is a switch failure. This works the other way around, as well. If the switch on the door does not cause the window to function, but the driver's switch does, that is an indication of a passenger door window switch failure.

Driving with a window switch is not likely to damage any other components, unless the window switch is constantly rolling one of the windows up or down. If the switch is constantly engaged, the corresponding window motor may become overworked and fail. Also, some vehicles will not turn off all accessories when the engine is off with the key removed, because the window switch is still being pressed. This can lead to security issues, theft, inability to raise or lower the corresponding window, and a dead battery.