One of the more aggravating things about owning and maintaining an ultra high-mileage Volvo (my Volvo XC70 has 350k kilometers) or similar car is that there are some features that you come to appreciate, but when they break, they don't contribute to getting you from point A to B. So, economically, do you replace them or not?
For example the headlamp wiper motors on a Volvo. I have always thought that those smaller wipers really help when driving through the snowy slop and they are missed when the motors invariably seize solid. But at something north of $200 to replace each motor, I see that as way too much when you consider the age and mileage of the car. Not that I didn't expect it, as I have had this occur at about 300k km on all but one of my white motor Volvos. Interestingly, all have been on the driver's side.
There are a number of small motor-driven devices on a modern Volvo: headlamp wipers, window lifts, rear wiper, etc. Each of these consists of a small can motor and a gear train consisting of plastic or nylon gears with an amount of light grease liberally applied. Not overly complicated. In all the cases of headlamp wiper and rear wiper motor failures, I have experience with the problem and it has not been the actual motor, but a seizure of a gear. This type of failure is a perfect candidate for a re-build and the following will outline a wiper motor I recently refurbished.
I will direct the reader to a suitable shop reference (i.e. VIDA) for the removal of the motor to be able to get it up on the bench. As a first step, remove the four screws holding the mounting bracket to the front of the motor and set the bracket and shaft seals aside.
The case of the motor is a straightforward plastic box with the cover held on by a series of flexible tabs. With the motor shaft pointing away from you and using a small flat screwdriver blade, gently pry the tabs away from the cover all the while applying upward pressure, so that the tabs release the cover. You need to slowly work around the rim of the cover releasing each tab in turn. I have yet to do this job without breaking one or two of the tabs, but you really don't want to do more than that. Ideally, you will be able to release the cover without breaking any.
Now that the cover is off and set aside with its seal, extract the motor shaft from the housing by wiggling the shaft to release it from the rack gear on the actuating arm. In my examples, the failure has always been the large gear seized to this plate so that when you remove the plate, the large gear comes away with it. In some cases, like this particular one, the whole gear train will come out with the plate. Take a close look at this point, remember where everything is and where it goes on re-assembly before you go any further.
Next, remove the actuating arm and its retainer. With that done, carefully remove the gear retaining plate taking care to not disturb the position of the underlying gears. If all the gears have come away with the plate, just remove the small un-seized gears from the plate and put them back in the case in their appropriate positions. Note, in this case, that it is the large gear that can't be removed, which seems to be typical.
Before proceeding further, make sure that all of the small gears are seated in their intended positions and free to move. You don't need to get crazy here. If any of these small gears are seized, it doesn't take much pressure to see that and free them. More than likely they will be fine and all you need to do is take your small screwdriver and re-distribute the light grease where it is needed.
Unlike windshield or hatch wiper motors, I've never seen the grease in these motors solidified. If you do encounter solidified grease, carefully remove each gear, one at a time and clean everything up. Also take a look at the wiper switches at the very bottom of the case to make sure nothing is broken or bent.
If you wish at this point and if all the small gears are clean and where they should be, you can apply 12 volts to make sure that the motor works. Prior to applying power, make sure the case is secure so that the small amount of torque that the motor will supply won't spill the whole mess onto the floor. Note that when you apply 12 volts, one lead (white) is on the middle contact in the plug and one is at one of the outer contacts (red and black). I believe that in this case, white is power, black is ground, and the red is the parking lead. Or I have the red and black reversed. I can never remember. In any case, easy enough to try it and see if the motor spins freely. Obviously, if anything has not worked as it should up to this point, then your failed bit is different then any I've seen and a trip to the junk yard may help in acquiring the necessary bits. Keep in mind, none of these pieces are available separately according to VIDA.
OK, so we should now have confirmed that the electrical motor is good, the wiper switches work, and all the small gears are free to operate. You should have found that re-distributing the original grease is adequate, but if not, reapply enough to adequately lube the small gears and set the case and its contents aside. Returning to the plate and large gear, try and remove the gear from the plate by hand. Mine was so stuck, so I had to lightly tap the gear with a small hammer to get it out of the plate. How a nylon gear can become seized to the plate makes no sense to me. With this design, it looks like it has to swell to cause the seizure. In any case, every one I've encountered has been like this.
Once the gear is removed, clean off the old grease from the gear and plate. The bearing surface on the gear itself is too small to alter, so set the gear aside for now. Taking the plate and some 200 grit sandpaper rolled into a tube (emery cloth or a Dremel with a sanding drum will work, depending on how much you need to take off the plate), sand/polish the bearing surface of the plate until the gear is free to move when placed back into position. Sand/polish evenly to maintain an even circumference. Now try to fit the gear, then go back to sanding until the gear fits and rotates easily. A little bit at a time is best, so take your time to get the gear to fit properly.
Also, make sure that you remove any sand or grit before you try each fitting. Cleanliness isn't necessarily critical in this application, but a clean job will allow you to maximize the life of the refurbished motor. Once the large gear turns smoothly in the plate and every thing is cleaned up, place grease in the bearing groove of the gear on the bearing surface of the plate and mount the gear in the plate.
Replace the actuating arm and its retainer by applying a bit of grease in the retainer where the arm is held. Replace the plate into the case, making sure that the axles of all the small gears return to their proper holes in the plate. Note that you also need to line up the retainer for the actuating arm with the hole for the wiper shaft.
Before re-inserting the wiper shaft, I applied 12 volts to get the motor and large gear to position themselves in their rest position. The alignment should look like it does in the picture above. Once you are satisfied that you are correct, push the wiper shaft from the backside through to the front, matching up with the rack on the actuating arm and retain temporarily it by installing the seals on the front of the shaft and case.
Before I installed the case cover, I once again applied 12 volts to the motor to verify that the motor, gears, and shaft, worked properly, then returned to their rest positions. Note that when you apply 12 volts, one lead (white) is on the middle contact in the plug and one is at one of the outer contacts (red and black). Once you figure out which way works, apply power to the other outer contact. This is the parking mechanism, so to make sure the everything is indeed at its rest position, you need to do this. Note the position of the cam on the wiper shaft and the actuating lever pivot on the large gear. Again, these are the positions of both at rest.
Now that that is set, reinstall the back cover ensuring that the seal is properly placed and that all the tabs are locked down. Re-install the mounting bracket (only one way works) and the now-working motor should be ready for installation back into the car.
At the price of a new wiper motor, I figured that my time exceeded $200 an hour. I have found that repairs of regular wiper motors are not dissimilar despite their separate motors and gearboxes. In these cases, I have found solidified grease to be the culprit and a good clean gets things working again. Generally speaking, in these types of fixes, getting the component removed from the car and then reinstalled is the hardest part of the whole procedure. Slow thoughtful going (or as my grandfather would say remembering that everything goes back together, the way it came apart) makes this effort well worth the time to take these apart, get them functional, and save some money in the process.
