Power windows in Toyota products use an electric motor to turn a window regulator; this motor can wear out slowly, or become saturated with moisture and operate slowly. Replacement will usually correct the problem, although in some rare instances moisture in the switch assembly has been known to mimic problems with the motor. The average backyard mechanic can correct a slow motor condition on a Toyota in about an hour.
Check the fuses for blown filaments by removing the fuse panel door and inspecting each fuse relative to the window operation. The fuses will be marked, and several could interrupt or cause problems with the electric motor that drives the window regulator inside the door. Replace any fuses that do not seat correctly or have blown filaments by pulling them out of the fuse socket and replacing them with new units.
Remove the switch assembly from the door panel by prying up one corner or side with a screwdriver, then pulling the assembly free. Most Toyotas use "pop-in" switches, which are removed in this manner. Place the voltage tester's positive terminal onto the positive contact in the switch (typically the terminal that is activated by pressing the switch) and ground the negative terminal of the voltage tester to the body of the car. Most testers come with clips, making this easy. Press the switch and watch the voltage on the display. The voltage should be 12 volts, and less means that the proper amount of energy is not making it past the switch. This could be due to moisture or a switch malfunction. Replace the switch by replacing the entire assembly at once, pulling the wiring harness adaptor plug from the rear and pressing it into a new assembly. Press this assembly into the door panel and test the window.
Replace the window motor by removing the door panel and unbolting the motor from the window regulator. This procedure differs with each model, but the standardised method of removal is to turn the arm rest bolts and interior door handle screws counterclockwise, then pull the panel away from the plastic pop rivets that hold it to the metal. Place the panel away from the work area. Locate the window motor, usually at the lower right of the window regulator. Remove it by unplugging it from the wiring harness, then turning the mount bolts counterclockwise. The motor will slide out from the regulator gears, and can be replaced with a new one.
Check the battery charge with the voltage tester, or more advanced equipment available at auto parts stores. A low battery, or a battery that is about to fail, can cause a slow window if the engine is not turned on. The amperage required to power the window will tax the battery beyond its ability to provide electricity. The repair is to replace the battery with a new unit, disconnecting the terminal bolts counterclockwise, then pulling the battery out of its mounting harness. The amount of power required to start the Toyota exceeds the window's power usage, so a quick test is to attempt to start the car. If it will not start, the battery may be at fault.
Disconnect the battery before making physical electrical repairs to the car.
Use extreme caution when working with a car's electrical system.