Wiper Motor Repair Tutorial

Hi Guys, I have decided to make a write up on repairing the wiper motor rather than replacing it. As some of you may know i live in the UK so replacement parts are much harder to get and a lot more expensive to ship over from the states. so i decided to attempt a repair on the motor myself.

The state my wipers were in...

I had High and Low speed but no park. which also meant that i had no intermittent as whenever the wiper relay module would click off the wipers would stop and go as they wished. After running through the trouble shooting steps from the EVTM and the repair to the wiper governor that Gary had written up i was still having the same issue.

This lead me to manually testing the motor in place without the wiper switch and governor using a length of wire and some crimp connectors to the battery. Again i was able to get high and low speeds but no park. This is the very simple drawing i made to tell me what pin does what.



To Park, the 12V power must go to the red pin and a jumper must be placed between the black and white (low) terminals.

The reason there is no park is because of the motor itself, there is an armature similar to a relay arm inside the motor that shorts the red and black pins, this black pin (through the governor) provides power to the white (low) terminal. The gear inside the motor ASSY has a notch that actuates this armature (the park position 'brush') thus when the motor is not in park the red wire is supplying power to the black wire that spins the motor in the low position until the gear actuates the armature removing the connection stopping the motor in the 'park' position.


The Tutorial; 


Step 1, remove the wiper motor from the truck

Step 2, Remove the 2 screws that retain the motor housing.













Step 3, Carefully remove the housing, don't be alarmed that all the brushes will ping lose, just be aware that the 3 springs are not attached and could go flying.

At this point you can put a multi meter between the red pin and the black pin and spin the wiper arm, this should give continuity (beep) at all positions and then be open circuit in the park position, however if the park isnt working then this wont be the case, the pins will be open circuit all the time.

Step 4, Flip the ASYY over, Remove the 5 screws that hold the gear ASSY in place













Step 5, slide the backing plate off the gear, note that there is a small bushing that can fall out that goes at the bottom of the motor shaft, this must be put back if it falls out.

You should now be left with something that resembles this;






















Step 6, you will see that on the backing plate there is an armature with a terminal either side,






















This is the reason why the motor does not park. This will have corrosion on it and must be cleaned to gain proper operation.

Step 7, Simply get some fine sand paper and gently clean the pads on the terminals and on the armature itself. there is no need to force or bend anything here. the sand paper should be small enough to just slide between the pads, it will be tight on one side but you can still clean it carefully. you don't need to go mad here, it should only take a few wipes with the sand paper to clean the pads.

Step 8, Start to re assemble the backing plate and the gear ASSY. Make sure that bushing is still in place at the bottom of the motor shaft! Put all the screws into the gear ASSY at this point.

To re aline the brushes simply use a small screwdriver or the probe of the multimeter to push the spring back into its guide and then slide the copper brush back in as well, then use the retaining clips build into the white casing to hold the copper wire to keep the brush back away from the shaft.




Step 9, Once the brushes are retained in place you can place the spindle into the hole, you will need to pull it out from the housing, don't worry its only the magnets holding it in! You may need to gently rotate the spindle to align the gears.

Before placing the spindle it is a good idea to check the circuit again for continuity on the red and black pins, the open circuit should now be at all but the 'Park' position. if it still doesn't stop beeping then go back and clean some more, manually move the armature while performing this test to make sure it could work then re assemble and test again.






















It should slide down and seat on the bushing in the gear ASSY, there will be a plastic tab protruding from the back of the unit. If this is not the case then you will need to start again from step 4  to put that back into place.

This is the spacing you should be left with once the spindle is back in place,






















Step 10, Now pop the wires holding the brushed back out of place, all the brushes should be touching the spindle now.

Step 11, Place the motor housing back over the spindle, make sure you align it properly and place it in quick, the magnets will pull it together and removing it will mean you need to remove the spindle and realign the brushes. It will likely leave a small gap between the housing the the ASSY, you should be able to press this together, you shouldn't need to force it, if it wont go then take it apart and try again!

Step 12, replace the 2 screws that hold the housing in place, be sure to put the ground strap back into place else the motor will not work!

Step 13, Put the motor back into the truck and test, you may need to put direct power to the low terminal for the first start to realign the brushes and the armature. once this is done you can put the plug back in and enjoy working wipers!!!


Hopefully this will help others who were in the same situation as me, replacing the motor may not be necessary! this only took me about 15 minutes to accomplish so with the tutorial instructions above it should be easy for everyone.  

Matthew - Well done!  

Would you like that to be put on a page to immortalise it?  I'm thinking it would be on a new tab, maybe called Park Repair, or Repairing Park Position, or somesuch on the page at Documentation/Electrical/Windshield Wipers.  What do you think?

Thanks for the great write-up Matt!     ... or elbow/heel touching. Whatever is appropriate in this age of Covid distancing.

This will be very helpful for many of us here.
Maybe Gary can duplicate it in the library.

Thanks! I think it would be a great idea to put it into a tab, it's such a simple repair that will solve the 'replace wiper motor' in the service books.

Gaah, you got me while I was pecking out my response!  😄

Thanks Jim

Something about epoxying the magnets back into the motor might be worthwhile too.

Matt - It's just gone 3 AM!  What are you doing up?

I'll see what I can do about that tab......  

I started to repair that motor at about midnight  then decided to do the write up while it was fresh Haha, absolutely going to bed now!!

Matt - See what you think now.  I'm not terribly happy with the alignment of the pictures and the text, and expect you to want some changes.  Just let me know and I'll sort it tomorrow.

Documentation/Electrical/Windshield Wipers

the alignments does need some work, depending on the device you are viewing on it looks different. this might have been my fault as i had to put lots of returns in my original post to get the text below the pictures, i've taken a couple of pictures of how it looks for me on my end.




I think it looks perfect on the mobile version of the site but on the computer it is a bit off, ill let you decide how you would like to lay it out, i can send over the full size original pictures if you'd like?

I put the pics side-by-side with the text I thought went with them.  But the mobile version doesn't support that, so they go serially.  However, with the extra width of the PC's monitor they get put beside the text.

Do you want me to put the pics in-line, meaning just as you had them originally?  I can do that and then there won't be much, if any, difference between mobile and PC.  Yes?

As for the pics, I just snagged the ones from your post.  But if you want to email the originals they might be better.

I think having them serially would look better and make it easier to follow, but it's up to you.

I have emailed you the link to my google drive where I saved the pictures I used, let me know if it doesn't work

I'll convert to serial and the link worked......  

Ok Matt, see what you think, please.  There are lots of options on how large to make the pics and I can easily adjust them.  So let me know what changes you'd like me to make.  It is your "page".

I think that looks perfect! easy to follow and read. if anyone else has any suggestions then feel free to chime in!

Thanks for the write up! I have one "dead" motor that I think I kept. Going to open it up and see what's wrong with it.

These motors are getting hard to find in my area. Not too many bullnoses or Aerostars at the PickNPull.

No problem! Please post back your findings

Nice job!
I disassembled mine when I powdercoated it and I will say if you remove the large magnets inside the canister, they can be a pain to reinstall with the clips.
Good timing on this thread as mine had been working but just the other day it wouldn't turn off and the intermittent functionality didn't work. On mine though if I rotate the dial in just the right spot it will so thinking mine is just a bad switch. If that doesn't do it, I'll be following in your testing process.

Just used this to do mine, thanks for the great guide! Only thing I would add would be to clean the commutator while it's apart just in case.

Mine is an original Motorcraft and the two main assemblies were "sealed" together by some kind of crimping process or tack welds, I couldn't tell which. Anyway, just drilled them out and then I was able to pry it apart. Was smooth sailing after that.