Wiper motor - reanimated!

[wild man]

The wipers have only ever worked on high setting since I have owned the car, and barely worked, at that. That is until about a week ago, when they stopped working altogether. Sometimes you could get them to move a little if you "helped" them with your hand, but that is not something that is easily done while driving in the rain. After removing the assembly and opening up the gearbox, I found no obvious signs of problems. So then I opened up the motor itself, and what I saw inside was not a pretty sight. That kind of rust never is. Although it looked like steps were taken to prevent water form entering, it had entered and did it's "dirty" work, anyways. The commutator surface was a burnt, black mess, and 1 of the 4 brushes (never saw a brush setup like that on a motor before) was frozen in it's guide. But it did have 3 good things going for it (I had no intention of buying a new assembly for the tune of 4 1/4). The windings were not toast, the magnets were intact, and the brushes still had some life left in them. I have before-and-after pics, but I don't know if it's possible to UL them to this site, as I have no place to put them where I can link to them.

Anyways, I wire brushed the rusted rotor, as well as the inside of the case, and then sprayed them with rust converter. I filed down the commutator until it was a nice shiny copper, removed the brushes and springs form the plate, cleaned them, and put them back in place. I then proceeded to repack the front ball-type bearing assembly, and filled the rear sleeve bearing area with grease, since I could find no felt ring, where one should have been, to soak with oil. I then used a generous amount of sealer on the motor when putting the case back together. The gearbox was then packed with grease and re-assembled, as was the rest of the assembly. At this point, I also took the liberty of re-soaking the bearing felts in the blower motor, while it was out. I am happy to report that my wipers now work fine on high, medium, low, and intermittent settings like they are supposed to.

[Icey1174]

You will find that many "broken" things on these cars just need some good cleaning and some TLC. Congrats on the work!

[ideola]

Nice writeup, thanks for sharing!

[wild man]

Let me add a few things that I left out in the 1st writeup, in case any1 wishes to "try this at home": (in case you didn't get it, that WAS a pun)

To do the commutator, I put the rotor into the chuck of a drill and spun it up while (lightly!) pressing a flat fine "needle" file against it until it was clean copper. I then went back-and-forth with some scotchbrite (while spinning it somewhat more slowly), to get a crosshatch pattern on it so the brushes will seat nicely. I did this for the blower motor also.

If any1 has a better method, let me know. But the "trick" I used to remove one of metal front bearing "shields" to allow repacking, was to use a straight mechanic's pick with a good point to pierce the metal via tapping with a small hammer, then with the pick in the hole at a low angle, pry up on the shield to pop it off. Then before putting it back in place, I tap down on it with the correct size socket (against a flat metal surface) to flatten it back out where the hole is, then seat it back into place on the bearing. After excess grease is removed, I apply sealant to the area where the hole is.

That should help those who may wish to attempt this fix. Remember that you must make sure that the crank is attached to the motor shaft at the proper position for the wipers to park correctly. I failed to do this the first time and had to take the assembly back off (and everything else that is in the way) and adjust it properly. I did this by plugging the assembly in while it was removed and observing where the wiper cranks stopped (parked) when shutting off the wipers. Unlike the motor crank, which moves in a circular motion, the wiper arm cranks only move about 90 degrees, or so, back and forth. The motor crank must be set so that when it parks, the wiper cranks are at the extreme end of their travel. There you go!

P. S. I forgot one small detail. There is a white plastic (nylon) "set' type screw on the gearbox that helps keep the end of the worm shaft centered, and it should probably be adjusted while the wiper assembly is out. Power up the assembly and turn it on low speed. While it is running, turn the set screw in until you can just hear it start to slow down the motor. Then back it out 1/8 to 1/4 turn and then apply sealant on it to keep it in position.

[OK-944]

Thank you! The wiper motor on my 85.5 sounds horrible, and only works on one speed (a very slow "high speed") as did yours prior to your fix. I was also put off by the high price of these motors (although there are some reasonable used ones around occasionally), but since you posted the above, I feel more encouraged about trying to fix it myself.

Sometimes I think I'll go ahead and buy the "official" set of 944 repair manuals, but I have a good sense that I can find all the info. I'll need on forums like this one. Thanks again!

[Icey1174]

The "official" repair manuals are nothing more then changing parts for the most part. These are truly fixing what is broken, not simply replacing it. This is the stuff that makes you really take pride in your work. You really fixed it, not replaced it. This stuff separates the men from the boys, the bolt on "Billys" and the true mechanics.

Great work and great write up. This is worthy of a submission to Clarks. Some pics and a very detailed set of instruction and you too will be infamous!

[The Glademister]

Originally Posted by wild man

The wipers have only ever worked on high setting since I have owned the car, and barely worked, at that. That is until about a week ago, when they stopped working altogether. Sometimes you could get them to move a little if you "helped" them with your hand, but that is not something that is easily done while driving in the rain. After removing the assembly and opening up the gearbox, I found no obvious signs of problems. So then I opened up the motor itself, and what I saw inside was not a pretty sight. That kind of rust never is. Although it looked like steps were taken to prevent water form entering, it had entered and did it's "dirty" work, anyways. The commutator surface was a burnt, black mess, and 1 of the 4 brushes (never saw a brush setup like that on a motor before) was frozen in it's guide. But it did have 3 good things going for it (I had no intention of buying a new assembly for the tune of 4 1/4). The windings were not toast, the magnets were intact, and the brushes still had some life left in them. I have before-and-after pics, but I don't know if it's possible to UL them to this site, as I have no place to put them where I can link to them.

Anyways, I wire brushed the rusted rotor, as well as the inside of the case, and then sprayed them with rust converter. I filed down the commutator until it was a nice shiny copper, removed the brushes and springs form the plate, cleaned them, and put them back in place. I then proceeded to repack the front ball-type bearing assembly, and filled the rear sleeve bearing area with grease, since I could find no felt ring, where one should have been, to soak with oil. I then used a generous amount of sealer on the motor when putting the case back together. The gearbox was then packed with grease and re-assembled, as was the rest of the assembly. At this point, I also took the liberty of re-soaking the bearing felts in the blower motor, while it was out. I am happy to report that my wipers now work fine on high, medium, low, and intermittent settings like they are supposed to.

After reading this post I was emboldened to try this myself and was successful getting the motor to run in a bench test. But I don't think it's quite reliable yet thought as it's quite loud when running. Sounds like the rotor is contacting the surrounding magnets. But if that were the case would it even function at all?

Also, I was curious exactly how much grease should be in the gearbox? It appeared to be full of contaminated, nasty gunk that was on the surface of the drive gear with the traces for the stop circuits. Obviously the whole assemble had laid in water for an extended period of time.

[rbuswell]

I am looking for expert advice on what is realistic. My car is a 1987 924S. I think the wiper mechanicals are 944. Both speeds work when turned on so I don't think there's a switch problem but neither of them are particularly fast. Is that normal for an old German car or could I be having some issues that going through the motor might improve? Thanks for your help.

[djnolan]

Having been there a couple of times over and over I can offer the following:

Buy a used motor and take it to an auto electric place for a refurbish of the brushes and bearings. One item that is NLA is the rubber brush mount suspension. So your rebuilder will have to improvise. Mine riveted it in place. This is needed to make sure the brushes make good firm contact.

Once you get it back make sure it is THOROUGHLY sealed with RTV (edit: liquid electrical tape) so water can't intrude into the motor.

The reason I say a used spare, is it is a major pain to remove the motor as the climate box and trim panel need to be removed first and having to test drive a partially repaired motor is not a good idea. They can quit like that, like in the middle of a rain storm, or when you most need the car.

[rbuswell]

Originally Posted by djnolan

Having been there a couple of times over and over I can offer the following:

Buy a used motor and take it to an auto electric place for a refurbish of the brushes and bearings. One item that is NLA is the rubber brush mount suspension. So your rebuilder will have to improvise. Mine riveted it in place. This is needed to make sure the brushes make good firm contact.

Once you get it back make sure it is THOROUGHLY sealed with RTV so water can't intrude into the motor.

The reason I say a used spare, is it is a major pain to remove the motor as the climate box and trim panel need to be removed first and having to test drive a partially repaired motor is not a good idea. They can quit like that, like in the middle of a rain storm, or when you most need the car.

OK reading between the lines, the wiper motor is known to run the wipers slowly if it needs to be worked over. Thanks for the advice on what to do next.

[djnolan]

Maybe first try some better wiper blades that don't drag as much and check the ground wire. The one you have could keep working for a long time. No way to tell for sure. But if it quits the new ones cost a fortune and the rebuilds are junk and the used ones are not likely to last too long either so a rebuilder is an option.

[rbuswell]

Originally Posted by djnolan

Maybe first try some better wiper blades that don't drag as much and check the ground wire. The one you have could keep working for a long time. No way to tell for sure. But if it quits the new ones cost a fortune and the rebuilds are junk and the used ones are not likely to last too long either so a rebuilder is an option.

New silicone blades so that's not it. They were slow before I put them on. I keep wondering if it's me and unrealistic expectations. My other cars are much newer Japanese drivers except for the 911SC. The wipers seem to go slower on the 911 too. Japanese cars seem to have the best electricals you can get so maybe I'm spoiled. I also wonder if the wipers will get better after I've used the car a while. It is in rehab after sitting for about 3 years.

[djnolan]

It may be worth posting a picture of the wiper motor assembly as not everyone is familiar with the 924S. There is a 944/1 electrical system and a 944/2 (post 85.5 MY) electrical system with significant changes. My experience is with the 944/2.

[spugeddy]

I successfully took my motor out, cleaned it up and got it working. There was a lot of rust and loose bits in that housing preventing it to function correctly. It is a little time consuming because you have to get the whole linkage out to get the motor disconnected, but I have heard they aren't making this part anymore so it would be good to keep yours cleaned and working properly.

There is a good youtube video on the whole process, in German, but you can do subtitles to your language.

[rbuswell]

Originally Posted by djnolan

It may be worth posting a picture of the wiper motor assembly as not everyone is familiar with the 924S. There is a 944/1 electrical system and a 944/2 (post 85.5 MY) electrical system with significant changes. My experience is with the 944/2.

Originally Posted by spugeddy

I successfully took my motor out, cleaned it up and got it working. There was a lot of rust and loose bits in that housing preventing it to function correctly. It is a little time consuming because you have to get the whole linkage out to get the motor disconnected, but I have heard they aren't making this part anymore so it would be good to keep yours cleaned and working properly.

There is a good youtube video on the whole process, in German, but you can do subtitles to your language.

I have been amazed at how readily available parts are out there for this car. Surprised that there aren't new motors or some cottage industry that has stepped in to keep them going. In any event, I've been adequately dissuaded from doing anything in the short run. I don't think my wipers are operating poorly enough to push it up the list of things I have to do right now. Thanks again for your help and this thread will be what I refer to when I have the time to tackle it.

[9FF]

Thanks for the write-up. Fwiw here is my contribution to this thread.

Over the years I have rebuilt a number of motors on these cars including the blower, radiator, roof and wiper motors, imo they are all doable by someone with average mechanical skills and the procedure for all of them is similar. If you know how to solder, peen and blind rivet, and are patient and work methodically it’s not that difficult. It may sound obvious but the best way to proceed is to dismantle everything, clean everything, see what has worn, and finally replace (or repair) the worn parts before reassembly. Don’t skimp, eg: replace bearings even if they look and feel ok, they have 30+ years of wear and you don’t want them failing a week after you rebuilt the motor. Same for the springs that push on the brushes. Be careful cleaning the commutator, best to leave it than use something abrasive, a mild cleaning paste (I use toothpaste) works well and is easy to clean off afterwards. New brushes will need manually bedding in, check YouTube for videos on that. You will also need a high-wattage iron to solder the tails of the brushes. I go overboard by blasting and powder coating parts that are subject to corrosion and using stainless fixtures, it’s not required. Here is an <old link> to a post on RL about some radiator fan motors I did many years ago, they are still running strong. A before and after picture.

[djnolan]

The later model wiper motors have a rubber brush plate "shock isolation" mounting that needs to be addressed, too. Wish I had a picture to upload.

[rbuswell]

Thanks guys!!!

[88Silver924S]

I didn't notice anyone mentioning this excellent YouTube video:

https://www.youtube.com/watch?v=eWpZI4KUrUk