Faulty windscreen wiper motors operate intermittently, or not at all. It can be particularly frustrating if the wipers gradually slow down, stop functioning altogether, then suddenly start working again, only to fail again the next day. There are a few simple fixes to eliminate this annoying cycle. By doing as many of these as you can, you will avoid having to dismantle and reassemble your motor over and over again, which is time-consuming and difficult.
Check all connections using a multimeter. This helps you identify exactly where the problem might lie, and pushes you toward an appropriate solution.
Rewire the unit so that it takes power directly from the battery. This eliminates the possibility that it is your wiring circuitry at fault, and not the windscreen wiper motor itself. You will need to install a switch on the dashboard to operate the newly wired windscreen wipers and wire it from the wiper blades to the battery using electrical wire. A length of no more than a meter of wire should be required.
Lubricate the components using electrical lubricant. This will require a dismantlement if you want to be sure you have covered all the relevant parts of the motor. To take the motor apart you must first remove it from its housing by following car-specific manufacturing instructions (check your car manual or try a Haynes or Chilton manual). Remove the circuit boards by lifting the side tabs with a small knife. Pinch the small, black button tab in the centre of the circuit board and lift. You will find that the board is soldered to the electric motor. Disconnect the joints by using your soldering iron (heating them will cause them to dissolve or melt). The circuit board lifts out completely. Unfasten the four screws holding the gear cover in place. You will see a yellow component (a gear). Mark its position and orientation clearly using a piece of chalk or small piece of easily identifiable tape in relation to the surrounding case so you won't forget how the two fit together during reconfiguration.
Clean the components carefully. Dirt inside the motor, on the brushes or in and around the electrical contacts can all cause the blades to wipe inefficiently, and the motor to exhibit a stuttering output.
Rectify corrosion in the system. Corroded contacts or wires will reduce the efficiency of the motor and cause intermittent or halting wiper blade motion. To remove corrosion, use a gel product such as Bilt Hamber's Deox-Gel, which is designed for rust and corrosion removal. Because the smallest amount of this available is in a one-kilogram measure, you may also want to use it to remove rust on other parts of the car, tools or machines. It is nontoxic, safe and biodegradable, and it does not destroy delicate steel wires, according to the company. Rust Release Super Gel, an acid-free jelly, is another excellent product to try, and has been specifically designed for rust removal in cars, as explained by their website.
Install new brushes. Replacing worn brushes, if this is identified to be a potential reason for the wiper blades not working, should rectify the problem. Look for products that come with a guarantee.
Resolder old joints within the motor. The area required can be located in the motor's circuit board. Look for fractured joints, worn sections and corrosion. Use a hand-held, household soldering iron (they look like a large pen) to resolder the joints. Allow them to cool, then reinstate the motor.
Buy a new windscreen wiper motor if nothing else works. This isn't technically a repair to the motor, but in the case of a broken or faulty motor that does not open up easily, purchasing a new one, or ordering one online from a reputable company (a low-cost example is eBay) may be the least time-consuming, most hassle-free option.
Using a soldering iron can be dangerous because it becomes very hot (over 93.3 degrees C Celsius) and create molten metal that can seriously damage skin if it comes into contact with your hands or arms. Wear safety gloves and cover bare skin. When looking for a new motor, avoid scrap yards. Old versions of motors, from older cars, may not have wiring that supports a standard intermittent setting.