Power windows became available on many luxury cars in the 1950’s and by the following decade, were found on many medium and even lower priced cars, as well.

   Some of the earlier systems relied on hydraulic power to raise the windows.  With those systems, an electric motor drives a pump.  With assistance from valves, the pump delivered pressurized hydraulic fluid to rams at each window.  Typically the hydraulic ram raises the window and a relatively powerful spring, in concert with gravity, lowers it, when the valve is opened to relieve the pressure in the ram.

   By the 60’s, however, hydraulic power windows were a thing of the past and almost all cars relied on electric motors to raise and lower each window.  Electric window motors and mechanisms are generally quite sturdy and reliable, but like everything else, they deteriorate over time.

   The two biggest enemies of electric power windows are corrosion and excessive heat. Corrosion comes from moisture in the air, in some cases, immersion in water.  Power windows motors are always mounted in the doors or between outer and inner body panels.  If drain holes in these areas get clogged, they can harbor significant quantities of water.

  As with any electric motor, the amount of heat generated by a power window motor, increases significantly, as the load, which it’s subjected to, increases.  The load increases, as resistance increases in the systems mechanicals by lack of lubrication.

   Anything that increases resistance on old mechanical components, such as old hardened gummy grease, distorted arms, broken rollers, bent tracks and so on, makes the motor work harder and hotter.

  In addition to the increased mechanical resistance, increased electrical resistance in the motors circuitry also generates added heat.  Loose connections and corrosion are the most prevalent causes of higher resistance.

  If you have a window motor that is tired or failed altogether, restoration is in order.

 Photo 1                                                    Photo 2

  Photo 3                                              Photo 4

 Photo 5

   Begin by removing the gearbox cover as shown in Photo #1.  The cover is held on by a single screw and may require some gentle prying after the screw is removed.

   Next, remove the driven gear (also called the second reduction gear) from the drive gear, as shown in Photo #2.  The driven gear, which is metal, simply lifts out, but sometimes it’s stuck and will take some effort to remove.  

Lift out the drive gear, which is made of nylon, as shown in Photo#3.  There should be three cylindrical pieces of nylon, located in the recess in the face of the drive gear, but these are frequently broken apart and unrecognizable.

The window motor directly drives a worm gear, which is machined into the armature.  The worm gear, in turn, drives the nylon drive gear, you just removed.  The metal driven gear (second reduction gear) that you removed earlier, sits in the recess, in the face of the drive gear and is locked in place by the threee cylindrical pieces of nylon.  In other words, the three cylindrical pieces of nylon act as keyways for the metal driven gear.

   The motor spins the worm gear and the worm gear turns the nylon drive gear.  The metal driven gear is sitting on a shaft on the face of the nylon drive gear and the two are locked together by the three nylon cylinders, so when the nylon gear spins, the metal gear also spins.  The metal gear actually raises and lowers the window.   Why not have just the nylon gear raise or lower the window?

   The metal gear is a second reduction gear that reduces the rpm of the spinning motor, increasing the torque multiplication and reducing the speed at which the window moves.

   And why is the nylon gear coupled to the metal driven gear, by the three nylon cylinders?

   The cylinders act as a shock absorber, helping to dissipate the sudden load generated when the window reaches it’s top or bottom.

   Without those cylinders, something in the window mechanism would break or wear out relatively quickly from the repeated impacts.

  Over time, the three cylinders get increasingly brittle and owing to the repeated loads they must endure, they crack and then break apart.   When this happens, you hear a “clack, clack, clack” sound, when the window is at the top or bottom and the motor is still turning.

    Eventually, the window stops moving altogether because withouot the three cylinders, the metal driven gear is n o longer lockedto the nylon drive gear.  When this happens, either the motor spins the drive gear, but the driven gear  remains stationary or the motor jams because of the broken – up debris.

   Photo #4 shows two nearly identical motors with the gearbox covers off and the metal driven gears removed.   The three nylon cylinders in the motor on the left have all but disintegrated into the gear box grease, while the cylinders in the motor on the right are intact.  Even if the cylinders in the motor look good, it is advisable to replace them, since they can fail in a relatively short time, in spite of their  seemingly good appearance.

  Most motors have alignment marks on the gearbox, motor housing and motor endplate.  If yours is not marked, use a small punch to mark it, so the parts can be reassembled in their correct orientation.

  After you remove the drive and driven gears from the gearbox,  and make certain the parts are marked for proper alignment, unscrew the two long bolts that hold the motor and gearbox together, as shown in Phoito#5.

  Next, separate the motor end plate, brush holder from the motor’s housing as shown in Photos #6.  There should be a thin paper gasket between the two and sometimes they are stuck.  If so, pry gently with a small screwdriver or tap lightly with a soft face hammer.

   Separate the motor housing from the gearbox as shown in Photos #7.  As with the endplate, the housing and gearbox may be stuck together, thus requiring some gentle persuasion to take apart.

    Slide the armature out of the motor’s housing as shown in Photo #8.

   If you motor is a permanent magnet type, like the one illustrated here,  it will take some effort to take the armature out.  Pull it firmly to overcome the force of the magnets that are bonded to the inside of the motor housing.

          The two brushes, which are held in place in the motor’s end plate, are normal wear items that should be replaced, in the course of the rebuild.  One is ‘soldered’on and can be ‘unsoldered’ with a soldering iron, as shown in Photo #9.  the other brush is welded on and can be clipped with wire cutters.  Set the brushes aside or later reference.

   As you will have noticed by now, the inside of the motor and gearbox, are quite messy.   The inside of the gearbox  was packed with grease when new and by now, some or all, has become solidified.

   In addition, as pointed out earlier, you will likely find broken plastic debris mixed into the caked-up grease.  The inside of the motor has to be full of black carbon dust, created as the brushes wore.  It is also likely that you’ll find rust here and there and a general coating of muck.

  To clean up the window motor parts, use a parts washer or soak them in a  cleaning solvent for a while .   After the parts are clean, dry them and blow them off with compressed air.

   Use a glass bead cabinet to lightly blast the motor housing, endplate and gearbox.  This cleans off any corrosion, solidified grease and other blemishes.  (EOP2)

Photo 6                                             Photo 7

Photo 8                                                     Photo 9

Photo 10

CHECK THE WINDINGS

    If you have a wound motor and have a break in the winding, the motor will not work.   Use a continuity tester to evaluate the continuity of the winding.  If there is a break, you will need to replace the armature with a good one or have the bad one rewound.

    It is also possible for the winding to have continuity and still be bad.  The wire that forms the winding must be insulated and if the insulation breaks down, there will be continuity, but little or no magnetism.   The wire is insulated with an electrical insulating varnish that deteriorates with excessive, prolonged heat.  If this happens, the armature must be replaced, rewound or reinsulated.

    While rewinding the armature with brand new wire, is certainly an effective route to take, it can be difficult to find someone capable and willing to perform this service.  To avoid having to  rewind armatures,  there is a very effective means to re-insulate the wiring.

   Begin by thoroughly cleaning the armature with brake cleaner to remove any grease, oil or contaminants that will inhibit adhesion.  Then thoroughly dry off with compressed air.   Bake the armature at 300 degrees F. for approximately 10 minutes to remove any moisture and get the winding hot.

    While the armature is baking, place enough electrical varnish in a pot, so you can totally submerge the winding and heat the varnish on the stove with the burner set at it’s lowest position.

    Dip the (still hot) winding into the container of hot electrical varnish and let it soak for 30 minutes.  Remove the winding from the varnish, place it on aluminum foil and bake it in the oven for 30 minutes at 300 degrees F.

  Remove the armature from the over after 30 minutes and let it cool.  Once cool, remove the varnish from the commutator and armature shaft with lacquer thinner or a similar solvent.

   In addition to testing the armature windings for continuity, you should also test to make sure the armature winding core doe NOT have continuity to the commutator as shown in Photos # 10.

   Finally, test each of the commutator bars for continuity to one another as shown in Photo #11. The commutator bars, like the windings, need TO BE continuous.

  The ends of the armature shafts must spin freely in their bushings, so it’s important they’re clean.   Briefly, wire wheel the shaft ends, as shown in Photo #12, to remove any glaze or other  foreign material.

   In order to clean and true the commutator surface, use a lathe, as shown in Photo #13 or mount the armature in the chuck of a variable speed drill,  clamped or mounted in a vise.  Use a fine file to dress the surface of the commutator and then compressed air to remove the filings from the armature.

With all the parts cleaned and dry, the armature tested and the commutator lightly resurfaced, you are ready to begin reassembly. (EOP3)

Photo 11                                                           Photo 12

  Photo 13                                                         Photo 14

Photo 15                                                      Photo 16

BRUSH PREPARATION

          As stated earlier, brushes normally wear out and should be replaced with new ones.   Purchase brushes slightly larger than required and cut them down top a precise fit.   As shown in Photo #14, use a micrometer to measure the dimensions of the original brushes to use as a guide in fitting the new ones.

   The brush holders in some motors are plastic.  When the motors were new, the brushes were slightly oversized and the plastic expanded to accommodate them.  By now the plastic is brittle, so make replacement brushes, just the right size to avoid cracking the plastic.

   At the same time, however, it is important to NOT make the brushes undersized.  If they are not snug in the holders, they can become cocked and contact the commutator at an angle.  The misalignment will provide less than 100 percent contact until the brushes wear down at the angle.

  In order to cut the brushes down, use a tool as shown in Photo #15

   The different sized grooves hold the brush securely, while it is passed over fine sandpaper, on a flat surface, as shown in Photo #16.

  Always purchase high quality replacement  brushes for your motor.

  Original brushes were predominantly carbon, with little or no copper.  New brushes have 70 percent copper content, which allows then to conduct much more efficiently. Better conductivity means lower amperage draw, which indicated the need for that large relay, fitted to the original motor circuit.

   In addition to cutting down the brushes so they fit their holders properly, you also need to cut down the ends.  When doing so, your objective is to leave them as long as possible, so as to prolong their lives, without permitting them to bind against the commutator.   Fitting the end dimensions is usually a trial and error process that requires installation and removal of the brushes several times.  (EOP4)

REASSEMBLY

Photo 17

Installing the brushes is somewhat of a tricky undertaking.  Both are held firmly against the commutator by small springs that are inserted into the brush holder before the brush goes in.  You must insert the spring, then the brush and then push and hold the brush against the spring tension.  While holding each side in, you insert the commutator end of the armature into the bushing in the end plate, so the commutator is between the brushes, Photo #17

This is an operation that would go easier if we had three hands.   You can make a tool to facilitate this process by using an old pair of snap ring pliers, Photo #18

 Once the brushes are correctly sized, you should lap then to the commutator.  To do this, install the brushes in their respective holders and insert the commutator into the endplate.   Be sure to put a dab of grease onto the armature shaft end. (Photo #19)  Synthetic disk brake caliper grease is recommended, in that it’s resistant to heat.

  With one end  of the armature shaft inserted into it’s bushing in the motor end plate, chuck the other end of the shaft into an electric drill.  Then, as shown in Photo #20, spin the armature while holding a commutator stone against the commutator.  A commutator stone contains abrasives similar to valve lapping compound.  The spinning commutator picks up the material and accelerates the wear on the end of the brush.  After a minute or so, the brushes are worn, so that they conform to the surface of the commutator.

When you’re finished lapping the new brushes, take them out and clean the commutator stone dust off everything.  Electrical contact cleaner, such as the Gunk brand aerosol spray ( Photo #21) works well for this task.

   After everything is cleaned up, you should dress the contact points.

   To prevent a meltdown from excessive heat, , the motor utilizes a simple, but effective electrical interruption system.  The circuit from one of the brushes goes through a set of contact points.  One of the points is held by what is called a bimetal laminate arm.  This is a small arm formed from 2 strips of metal, each having a different rate of thermal expansion.  If the motor gets very hot, the bimetal arm also gets hot.  Because one metal strip expands more than the other, the arm curls and in the process, separates the two contact points.  This opens the circuit and prevents the motor from continuing to operate.

  As with the contact points in your car, the mating surfaces of the motor’s points can become corroded and irregular.  To fix this, fold a small piece of #600 grit or finer sand paper, so the abrasive material is on both sides.  Spray the paper with a little electrical contact cleaner to act as a lubricant and insert the paper between the two points.  Move the paper back and forth several times to clean up the point surfaces (Photo #22)

    Just as you did after lapping the brushes, use electrical contact cleaner to clean the points and surrounding area of any sanding dust or other impurities.

SOLDERING IN PLACE

  The next step is to solder the wire leads coming out of the new brushes to their respective spots.  As shown in Photo #23, use a miniature wire wheel in a rotary tool to clean up the areas where  the wire leads need to be soldered, in order to promote adhesion.  Give the area a good blast of compressed air or electrical contact cleaner after wire wheeling to assure there is no errant debris.

  New brushes come with rather long leads that you usually have to cut down slightly. The goal is to make the leads long enough to accommodate the travel of the brushes as they wear, but not long enough to get in the way or come in contact with anything else.  Sizing the leads correctly is particularly important with wire wound motors because with this type of motor, the long bolts holding the motor housing, end plate and gearbox together, are quite close to the leads.  If one of the bolts touches one of the brush leads, it will create a short circuit.

  After you have trimmed the leads to their proper length, you need to solder them in place, as shown in Photo #24.  It is important to use silver solder, rather than regular tin based solder because the silver has a higher melting point.  Remember to use silver solder flux with the silver solder.

(EOP5)

Photo 18                                            Photo 19

Photo 20                                             Photo 21

Photo 22

  You are now ready to install the brushes and armature into the end plate for the final time. Don’t forget to again lubricate the armature end of the shaft with some high temperature grease.

INSTALL THE ARMATURE

The next step is to unite the end plate / armature assembly with the motor housing.  This is tricky with a permanent magnet motor because the magnets bonded to the inside of the motor housing can quickly yank the armature out of the end plate, when you start to insert the armature into the housing

   Make sure the alignment marks are lined up when you the housing into the end plate and don’t forget the gasket that goes between the two.

Also remember that the magnets are not longitudinally centered in the housing (They are closer to one end than the other, as shown in Photo # 25)

When assembled, the magnets are closer to the end plate than to the gear box.  This allows the armature windings to be fully encased by the magnets for maximum efficiency.

  The best way to put the housing and end plate armature assembly together tis to constantly push the armature and end plate while manipulating the housing.

  Hold the armature/end plate in one hand, squeezing the two together.  As you start to insert the armature in the housing, put your other hand into the as far into the housing as possible until you reach the armature shaft coming in from the other side.

Use one hand to push the end plate onto the armature and the other hand to push the armature onto the end plate, while using fingers from both hands to slide the motor housing down over the armature as shown in Photo #26.

    When the armature end plate assembly is fully inserted into the housing, it will tend to stay in place until you bolt it all together.  As shown in Photo #27, put a light coating of high temperature grease on the portion of the armature shaft that rides in the gearbox and on the shafts end.

  Install a new gasket on the gearbox housing as shown in Photo # 28 and slip the housing over the armature shaft.   Make sure the alignment marks line up and then install the two long bolts through the end plate to hold it all together.

 Some power window motors utilize an o-ring in a groove on the armature shaft to keep grease in the gearbox from entering the motor.  If your motor has one, you should replace it at this time.

There is an adjustment screw in the gearbox housing that is used to adjust the endplay of the armature shaft.  If you have not changed the end plate, motor housing, gearbox or armature, then you should not have to make any adjustment.

If any of these parts have been changed or the adjustment was bad to begin with, then you should adjust the shaft position.  Loosen the adjustment screw locknut, turn the adjustment screw in until it contacts the armature end as shown in Photo #29.  Then, turn it out ever so slightly that there is no discernible endplay, but at the same time, the shaft is not binding or dragging on the screw. Tighten the adjustment screw locknut to hold the screw in position.

  Use a liberal amount of grease to coat the inside of the gearbox, as shown in Photo #30.  White grease is preferred because of it’s tendency to have less drag on parts.

NEW SHOCK ABSORBERS

  If the three cylindrical nylon shock absorbers, described earlier are broken, they must be replaced.  But even if they look ok, it’s a good idea to replace them anyway, since their failure is almost a certainty. (EOP6)

Photo 23                                          Photo 24

Photo 25                                          Photo 26

                 Photo 27

               You can buy replacement shock absorbers from a number of sources, but as shown in Photo #31, he cuts three new absorbers from his own stock. The next step is to liberally lubricate the  inside of the nylon drive gear with white grease.  Then, insert two of the cylinders into the nylon drive gear, place the metal driven gear part of the way in, and simultaneously wedges the third absorber in while pressing the metal gear into place.  As shown in Photo #32, it is helpful to use a small screwdriver to help force the third shock absorber into place.

  After the two reduction gears and three cylindrical shock absorbers are put together, place the entire assembly into the gearbox as shown in Photo # 33.

   Pack some more grease into the gearbox, so everything there is well coated.  Then, as shown in Photo #34, reinstall the gearbox cover.  Before reinstalling the motor in the vehicle, it is advisable to bench test it.  Use a car battery to make sure the motor spins freely in both directions, as shown in Photo #35.

    Also, listen for any unusual sounds as the motor spins, as that would indicate a problem.   If it sounds like the motor is straining, try loosening the armature shaft adjustment screw slightly.   Turn the screw in or out listening to the motor.  The screw places the armature in the center of the windings, which is where they should be.

     After everything checks out, the final step is to refinish the exterior of the motor.   Usually the motor’s housing was painted semi-gloss black, while the end plates were left natural.  In some instances, the end plate was silver cadmium plated.   Some people like to paint everything to prevent corrosion and figure that since you can’t see it after its installed, the deviation from the ordinary doesn’t matter.  Others prefer to duplicate the original configuration of their motor and paint only that what originally painted.  Regardless of how you decide to refinish your exterior, the rebuild should last a good while.

INSPECT THE ENTIRE SYSTEM

When restoring a power window motor, don’t forget to inspect the remainder of the entire power window system.   Motor failure is often the end result of a problem that lies elsewhere.   Take a careful look at the wiring that feeds power to the switches and motors in your car.   Replace any corroded, frayed or otherwise damaged wiring.  Repair any loose connections, bad relays or sloppy switches.  If you have a bad switch and can’t find a replacement don’t despair.  Bob Clayton can restore most automotive switches and he does it at a reasonable price.

          In addition to inspecting the electrical components in the power window system, you should also evaluate the mechanical components.  Petrified grease in the window tracks or regulator assembly dramatically increases (EOP4)

Photo 28                                                 Photo 29

Photo 30                                           Photo 31

Photo 32                                           Photo 33

Photo 34                                                 Photo 35

the load on the motor and will accelerate its failure.  Also, look for distortions, breaks or other abnormalities in the various parts that compose  the window support and movement assemblies.  Like hardened grease, these will require the motor to work much harder than it should and  ultimately lead to failure.

SOURCE

Bob Clayton

611 Eva Kennedy Road

Suwanee, GA