85-91 Wiper Motor Rebuild

[Doppleganger]

The following pics and descriptions only apply (to my knowledge) to 85-91 SB wiper motors. I started with 3 motors and chose the worst one to rebuild. With it on a bench and no transmission connected, it ran at about 20% slow and a tad more more on hi. Keep in mind these are motors that are close to 40yrs old that came on trucks with 12 month warranties. I dont think these were ever meant to be serviced, which made the end result of this even better. Hopefully this is of some help to someone. This is an extreme overhaul, one I doubt most would ever need to do. Enjoy.

1-2. Overview

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3. Drill out the 10 shell rivets. The steel is very thin so you dont want to remove anymore than you have to. 19/64 is a perfect size, 5/16 works too. Then gently use a small flat screwdriver to pry it apart.

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4. The dirty secrets. You can see on the top half, the rib on the gear going from 9 to 1:00. Thats what triggers the parking switch. On the bottom half, the 2 magnets are kept in place by 2 spacers - one on top and one underneath. The one on top was ajar and allowed one of the magnets to attach itself to the armature, effectively sandbagging it from moving.

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5. The gear shaft is held in with 4 washers and a snap ring. I used the .040 pins in my snap ring pliers to remove it. Careful not to tweak it - although its easy to bend back if you do. The shaft rides in a pressed in bronze bushing. You dont want to mess the bushing up. Its a tight fit so any burrs, shavings, dirt, etc and it isn't coming out. Use a scotch brite and twist it like you're polishing a bullet. A tap from a rubber handle or dead blow and it will then come out no problem.

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[Doppleganger]

6. This is the order in which the washers are installed.

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7. Remove everything inside. The white plastic on the left side is the brush holder. On the 3 I have dissected, that plastic piece was broken on 2 of them, resulting in a brush spring losing tension (and low or high speed) . The worm gear is caked with almost 40 yr old grease with the viscosity of clay. There was also a ton of shavings from brushes, dirt, etc. I swabbed the commutator (where the brushes ride) with a q-tip and contact cleaner. That bronze looking ball on the motor shaft is a bearing - I removed it just to clean the shaft - dont lose it. The lash adjuster had a plastic cap on the end where it meets the end of the motor - this broke apart and came off. I am replacing it with a vac cap (will see that at reassembly).

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8. A closer look at those brushes. I also took this pic so you could note how and where the brushes are routed. Also note the II markings for orientation. (A) shows a rivet - there is one at 2 and another at 7:00. On 40 yr old plastic, these are areas of stress and breakage. This plastic doesn't flex or crack, it crumbles - like old bakelite. (B) is a tiny tab that the brush spring is wound against. These break off, resulting in a loss of tension on the brush, and a loss of low or high speed.

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9. Remove the parking switch by depressing the tab (A). Goes back in the same way. I pulled it because the case needs a more thorough cleaning.

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10. Because this one was in such bad shape, I wanted to see what was behind that brush holder, so I drilled out the (2) 3/32 rivets -carefully- with an 1/8" drill. One plastic corner was already cracked / separating from being old plastic with the stress of a clamped rivet, so was going to need replaced anyways. I also drilled out the bottom magnet bracket as well - due to rust and corrosion. I also removed the brushes / connector. Only thing holding it in is a tab in the front and a tab that clicks into the rear housing (will show this more at reassembly). It basically just sits in a slot. This also allows inspection and cleaning of the electrical contacts.

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[Doppleganger]

11. Nasty. That dark fan looking area is a sealed charcoal filter and around it (cant see it for the corrosion) is (6) .032" holes apparently for drainage. In the very middle - down inside is a bearing about the size of a watch battery. I pulled it out to clean - but dont lose it! Can also see the heavy corrosion on the brush contacts.

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12. With the end housing off, you can see better where and how the brush plug end mounts.

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13. Both outer shells have these 2 tabs (A) - they will need to be bent out of the way (B) - and then bent back at reassembly. Crazy way to do business.

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Now to the other half....


14. With the gear out of the housing, clean all the old caked grease and shavings out. I put it along with everything else plastic, into a qt jar with hot water and Krud Kutter. Let it soak overnight, then an old toothbrush to clean the grooves out. Worked very well. You'll also note the bronze bushing I mentioned earlier it rides in.

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[Doppleganger]

15. This is also when I drilled out the rivet holding the ground strap in. I personally dont like these types as the actual contact surface at the rubber mount is thin and easily disturbed. I prefer to use an actual grounding strap from the case to the firewall. Much of this you will never need to do - again, because of the sad shape of this one, I'm going all out.

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16. The shell is stripped and ready to be blasted. I inserted a bolt and washers through the bronze bushing to protect it from any media damage. Worked very well.

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[Doppleganger]

We're getting there.....

17. Was quite a mess to blast and ALOT of peaks and valleys to miss. I actually blasted them again after this pic, then dropped them off at the platers.

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So while they are at the platers, time to attend to the peripherals.

18. The contacts in the plugs (power/brushes and the park switch) were heavily corroded. I had wanted to pull the terminals out of the housing for better cleaning on both, but the build up was so thick and its 40yr old plastic, I didn't want to risk it. So I used a Dremel with a small brass brush. A thin film of dielectric grease will follow. The park switch contact was also corroded, so I used a small diamond file to clean it up.

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19. Even after soaking overnight, the graphite shavings from the brushes were still there. A q-tip with some contact cleaner got it out.

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[Doppleganger]

20. A newer nickle passivate formula that is 8x more corrosion resistant than what was used 2 yrs ago. Plater told me the original finish was more than likely a hot dipped process that was ok, but nothing like this.

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21. I taped off the insides and sprayed it with a self etching primer and 3 coats of satin black enamel.

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22. Time to start putting things back.

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[Doppleganger]

23. New firewall seal PN 20489125; new mounts OER 4910180; 10ga wire w/terminals; (10) 1/4" bolts with lock washers; 1 vac tip to replace plastic tip on lash adjuster. The 2 brackets for the magnets were stripped and replated with black zinc phosphate.

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24. Bottom magnet bracket reinstalled (riveted). Note the tiny slot (A) where the lash adjuster's tab sits.

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25. This is a mock up of how the magnets go in - do not install them yet - this is just a cutaway cheat view.

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Now here is where it gets fun - picture the game Twister, only for your fingers. We are going to reassemble the brushes, springs and actuator....and get them in place without anything falling out.

Do NOT have the magnets anywhere near this yet - we have enough issues without them. If you have not done so, grease the worm gear on the motor actuator.

 

[Doppleganger]

26. The assembly of the brushes to the rear housing.

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27. Set the armature into the rear brush housing.

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[Doppleganger]

28. Using a tiny screw driver (I used a dental pick with a hook on it), wind the brush springs ccw and hook them behind the tab. Be careful not to pinch the brush wires. Might have to angle the springs almost off their pins to get the spring end into position.

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29. *2 pics did not come out* - but WITHOUT THE MAGNETS ANYWHERE NEAR THE HOUSING, set the armature / brush assembly into the housing with the riveted lower magnet bracket. Make sure the rear brush housing aligns with the slot between the shell and the 2 tabs you bent out earlier.

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30. Hold the assembly in place while you place one magnet at a time on the sides of the armature - making sure the magnets rest against the lower bracket (as shown is step 25). Once both magnets are in place, install the top bracket-spacer between the 2 magnets. The magnets will be all but touching the armature (its a very tight-close fit).

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31. Reinstall the stop switch - be careful not to tilt the assembly to the point the armature slides or falls out. We're almost there.....

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[Doppleganger]

Now to the other half.....



32. Smear some grease on the shaft and teeth of the nylon gear and press it into and through the bronze bushing.

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33. Replace all the washers in the order they were in (see pic 6) and reinstall the snap ring.

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34. Set the gear half of the housing on top of your assembly, making sure the rear slot aligns with the rear housing.

I angled it so the back seated first and to keep the gear side's metal housing from dragging across the motor as the 2 very strong magnets in the assembly WILL try to lift out if given the chance.

Start 3-4 screws/nuts to keep it all aligned and together, then gently turn it around and with a (hefty) needle nose or some lineman pliers, bend the 4 tabs (2 on up and 2 on lower) back down like they originally were (picture 13).

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[Doppleganger]

35. Once all the screws are in and tight, reinstall the plastic cap (one push pin in the middle is all that holds it), the spindle cap, isolator cushion, and firewall gasket.

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[Doppleganger]

36. Finally, the new mounts and ground (if necessary). The original ground strap is permanently crimped onto the rubber mount, so to replace the mount, a ground strap is needed. I have seen the mounts for an old Nova wiper has a longer crimped strap, but they were out of stock, so I made one for functionality (10 ga wire). In the past with a similar style motor, I have also used a ground strap from the wiper housing to the firewall as well (which I like even better).

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[Doppleganger]

The final test was this: this particular motor ran at about 20% of low and very little difference on high. Now it runs like a raped ape. I have never had one so strong and quiet. I know its not hooked up to anything but it wasn't when I first tested it either. Night / day difference. I'm hysterical with how it came out, but should be noted that 3 motors were needed to do this one, because the plastic brush housing was broken on 2 of them. I had about $100 (not including 2 extra motors) in it, 2-3 hrs of time, but I kind of went alot farther than most will ever have to. I did see one place online offering rebuilds of these for $350, and their plans were pretty basic.

I've got a line on 3 more motors so going to build a couple more. If any other pics are needed, maybe I can get them then.

 

[SirRobyn0]

I've had a rough week at work, so when I can think again I'll probably ask you a few questions, but for now I just want to say that to anyone thinking of rebuilding their wiper motor, please, please replace the ground like Chris described, even if yours looks ok. I cannot begin to tell you the number of times I've seen bad grounds prevent proper operation. Some of those ground looked like they should be alright.

Dielectric grease. I'm in love with that stuff, seriously guys put it on the connector terminals. Not just for the wiper motor but for any connector terminal or bulb you replace. It helps make sure there is a good contact and keeps moisture out preventing potential future problems.

Also I think this should be a sticky. I've certainly answered my share of wiper related questions and it would be great to have this where it can be found again with ease. I'll tag a couple of the guys that could do this @bucket @HotRodPC

 

[ali_c20]

This is awesome work. The motor is better than new.