Servicing the windscreen-wiper mechanism

windscreen-wiper mechanism

Here you can get Servicing the windscreen-wiper mechanism.

The windscreen-wiper mechanism needs little maintenance. At service intervals drip a little oil down the wiper spindles from outside. If they stick, the motor could burn out.

A pushrod linkage

Most problems arise in the linkage , of which there are two types — a rack and wheelbox and a pushrod. The rack-and-wheelbox linkage has a long, flexible rack — a rod with a screw thread — encased during a tube and pulled back and forth by the gear and connecting rod of the motor.

A rack-and-wheelbox linkage

Wheelboxes (usually two) mounted on the tube each have a gear wheel that meshes with a stretch of exposed thread on the rack. The wheels convert the rack movement to the swinging action of the wiper arms mounted on the wheel spindles.

The other type of linkage has a pushrod pivoted to the gear crank. The pushrod pushes and pulls a rigid horizontal link rod (or two parallel rods) with a wiper-arm spindle at each end.

Servicing the wiper linkage

A wheelbox mechanism can become prone to sticking, or the wheels can wear and permit excessive play in order that the wiper arms move too far. To check whether a wheelbox is sticking, lift the wiper arms off the screen and take away the motor gearbox cover. Unscrew the nut locking the tube to the gearbox, and loosen the rack from the rod by removing a circlip and washer. Lift the rack clear. Hook a spring scale to the top of the rack, hold the tube and pull the rack until the wiper arms move. Measure the load of the pull.

The force needed shouldn’t be quite 6 lb (2.7 kg). If more force is required , the wheelbox and rack may have lubrication, or the tube could also be curved too sharply faraway from the motor. No bend should have a radius smaller than 9 in. (230 mm). you’ll shape the bend by hand. To lubricate the rack, withdraw it from the tube and grease it with high- melting-point grease. When rethreading, reposition it in order that the unworn threads are against the wheelbox gear wheels.

Lubricate the wheelboxes with the rack removed. begin the wiper arms and therefore the nuts securing each spindle, noting how washers and spacers under the nuts are arranged. Undo the two screws holding each wheelbox together and pull out the tube from each side. Pack the boxes with high-melting-point grease and reassemble.

A spring-clip wiper arm

If the wheel teeth are worn, turn the wheels through a half circle so that unworn teeth mesh with the rack. On a pushrod linkage, the wipers lose efficiency because of wear or damage to the linkage pivots. Replace any faulty parts.

Electrical faults

If the wiper motor remains dead or blows the fuse repeatedly, look over the wiring for poor or broken connections. If you discover none, use a circuit tester to see if current is reaching the motor. Clip the lead of the lamp to earth and hold the probe to the live terminal of the motor. If there’s current, the tester will light.

If it doesn’t , check if current is reaching the switch . If it is, look for a wiring fault between the switch and motor or within the switch.

What is Wiper Motor

The car wiper motor is that the component that powers the windshield wipers. as it spins, a mechanism built thereto rotates a gear , arm and, finally, the windshield or windscreen wiper blades. The wiper blades then rid the windscreen of water, snow, dust, or the other debris which will affect visibility when driving.

Car wiper motors form part of the wiper system. Because they help clear the windshield, they’re usually viewed together of the car safety components. Other parts of the wiper system include wiper linkage, wiper washer pump, and wiper switch. a number of these parts, like the wiper switch are placed near the driver, but where is that the windshield wiper motor located?

The electric motor assembly is usually found within the engine bay and often mounted firewall. From there, it connects to the parts that make the wiper linkage, helping to transmit motion and move the wiper arms and blades. The image below shows the windshield wiper motor location.

Although the standard location of a wiper blade motor is the engine bay, just below the wiper cowl, it’s not the only place to find it. Some cars such as hatchbacks, for example, are fitted with rear wipers. In addition to the front wiper motor, these will also have a separate rear wiper motor or what’s often called rear window wiper motor.

The conventional front or rear windshield wiper motor is an assembly of metal and plastic components. Costly models feature more metal parts than plastic, making them more robust and durable. In terms of design, wiper motors mostly differ in the gear arrangement, control mechanism, and transmission parts.

Removing a windscreen wiper motor

Disconnect the battery . Remove the electrical connections from the motor , preferably labelling them so that you’ll refit them to the right terminals. With a rack -and-wheelbox system, disconnect the rack from the motor gearbox and unbolt the motor. With a pushrod system, it’s usual to require out the motor and linkage in one piece. Often they’re mounted together on a plate which will be unbolted and removed.

On some cars you unbolt the pushrod at the motor spindle , remove the bolts that hold the motor and lift it out on its own. Before removing the motor and linkage, free the wiper spindles by removing the arms and unscrewing the spindle nuts. Note the position of any spacers and washers. Mark the linkage to point out how its parts are angled when the blades are within the park position.

If the motor failed when the wipers weren’t parked, mark the positions of the blades on the windscreen also because the angles on the linkage, as a guide when refitting. With the mechanism removed, disconnect the linkage from the motor.

Fixing the motor

Two types of Lucas wiper motor are in general use on English cars. Other motors are very similar, but you’ll not be ready to get new brushes or other parts for them. If you can’t get parts, buy and fit a new motor.

A wound-field motor

The earlier (wound-field) Lucas motor is square. remove the long bolts securing the endplate. Pull the fibre lock plate free from the brushes, open the jaws of the spring-loaded brush holder and slide it off the commutator. Look at the brushes – if they’re worn right down to about ; in. (3 mm), fit new ones, ensuring these slide freely. Use a fine file to remove any roughness.

Take out the armature and main gear wheel, and clean them with methylated spirit on a lint-free cloth. If the commutator is slightly burned or corroded, clean it with fine emery cloth; if however, it is badly pitted or scored, fit a new or exchange motor. If the gear teeth are worn, fit a new gear spindle. Reassemble the motor, packing the gearbox with plenty of high melting-point grease.

A permanent-magnet motor

The casing of the later ( permanent-magnet ) Lucas motor is round. Before you unbolt the casing mark its position on the gearbox. If you replace it the wrong way round, the motor will tum backwards. There may be quite two brushes if the motor has quite one speed. Inspect the brushes, and if they’re worn to in. (3 mm), fit new brushes and holders. Remove and clean the armature and main gear with methylated spirit on a lint-free cloth. The gear has a dished washer under it; refit it the proper way round. Clean the commutator with fine emery cloth.

If you’ve got to suit a replacement gear, buy a replacement with the same sweep angle, which is marked on the wheel -110 degrees, for instance. When you reassemble the motor, the brushes need to be pressed back to their holders while you fit the commutator. Tie them back with 4 in. (100 mm) lengths of 5 amp fuse wire. Twist the ends and let them stick out.

Push within the commutator until it just enters the space between the brushes, then take off the wires and slide the commutator home. On some makes of motor, brushes are soldered into place. Solder one brush at a time. Cut off the old lead, carefully noting its route, and match it with the new one. Melt a touch solder on a new lead and the contact point, then solder on the lead. Do not let solder line the lead and stiffen it. Some motors have exterior screws for adjusting armature end float (that is, lengthwise free play), which should be only fractional. Other motors have springs to require up end float.

Refitting the motor

When reassembling a pushrod linkage, use the guide marks you made to position rods at the correct angles.

Once the motor is back in place, test the wipers with the blades lifted off the screen. Then wet the screen with the washer and test with the blades in the wiping position.


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