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Unread 04-06-2007, 09:27 PM   #1
gomes512
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1994 ZJ 
 
Join Date: Nov 2005
Location: Des Plaines, IL
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Save $ on rear wiper motor

This was on my 1994 Grand Cherokee. I hear these motors are relatively the same all the way up to the WJ's and shared across many other SUV brands.

In this write-up I will show you why the rear wiper motor seizes and how to attempt to repair it.

Seizing is due to corrosion of the wiper arm rod to the shaft housing. Water ingress into the housing shaft allows for the corrosion. There is a small rubber o-ring at the end of the housing but over time, as with all rubber, it dries and shrinks. As the corrosion builds up the motor will gradually slow down and eventually it gets so bad that the wiper arm rod completely seizes to the housing shaft.

I followed the Hayne's manual for instructions on how to remove the motor from rear lift gate. Remove the screws holding the trim to the hatch and carefully pry it away. I removed the wiper arm from the shaft, unplugged the harness connector to the motor and unbolted the motor from the hatch. JF member fluffy2560 warns to be very careful removing the harness connector as the locking tab easily breaks, if it does use a ziptie to later secure both connectors.


I carefully removed the circuit board cover by lifting the tabs on the cover with a small knife.


I was greeted with this sight, I pinched the little black button tab in the middle of the circuit board and lifted it up. The board is soldered to the electric motor.


Since I lifted up the circuit board I simply touched the soldered joints with a soldering iron for a few seconds and each contact disconnected itself once the solder was melted. You can also use a solder sucker here.


Free each contact of the motor and then lift out the circuit board


Here is a view of the opposite side of the circuit board. Make sure not to push in the four pins located to the right (they will have dielectric grease on them).


Next take a 9/32 bit and unscrew the (4) screws holding the gear cover in place. READ NEXT SECTION BEFORE CONTINUING.


You should see something like this. VERY IMPORTANT: Make absolutely sure that you mark the position of the yellow gear in relation to the case. If you don't you will have a headache trying to find the original starting position. The metal brass plate located on the gear is the forward/reverse contact, do not remove it.


Most likely the arm rod will be seized in place, use a hammer and hammer the end of it. JF members stormer1092 and flm both suggest heating the arm rod housing with a torch for units with really bad corrosion.


Right before you will run out of anything to hammer the o-ring retainer will come loose. Save that piece along with the o-ring that may or may not come out at this point and continue hammering if need be.


Last edited by gomes512; 07-22-2013 at 12:57 PM.. Reason: Additional info
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Unread 04-06-2007, 09:28 PM   #2
gomes512
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Location: Des Plaines, IL
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The gear will come out in this fashion along with the shaft when you hammer.


Here the gear and rod have come all the way out (just pull it out). Notice the dark bands on the rod, that's the problem area. Clean the rod with carb/choke cleaner and use a metal brush.


Corrosion on the rod also indicates corrosion on the inside of the shaft housing. There should be a small black o-ring on the inside end of the cone, save it so you can compare at your hardware store to get a new one. Use a metal brush to thoroughly clean the inside of the cone (yes I had a heck of a time pulling that brush in and out of the cone). JF member ZJfreek suggests using a 9mm (or .38spl /.357mag) barrel brush to clean out the shaft.


Pull out the brush and spray down the inside of the housing with carb/choke cleaner and make sure all metal shavings/dust/dirt have been removed. Roll up some paper towels and pull them through to ensure a clean inside.


Using a flathead or knife, apply a large wad of grease on the inside of the hole in the housing. I would recommend a silicon or very wash out resistant grease in this application. Then take the rod lightly cover it in grease and push it all the way through and wipe off the excess.


Before you push the rod all the way to the end, ensure that it spins with little friction when it is almost entirely in the housing. This was the whole purpose of the project. Now push the gear all the way down and MAKE SURE IT IS IN THE ORIGINAL POSITION that you marked earlier (didn't you?). Notice in this pic the brass faceplate on the gear is missing. Don't make the mistake of removing it like I did.


Take the circuit board and lightly apply dielectric grease to the four pins mentioned earlier. DO NOT BEND THEM DOWN or they will no longer make proper contact with the brass plate on the gear.


Lastly, apply dielectric grease to the brass plate and the yellow gear to reduce corrosion and wear, respectively.

Put the gear cover back on, carefully snap the circuit board back on and touch the motor contacts with a soldering iron again to resolder the connections and put the circuit board cover back on. Don't forget about the rod o-ring and o-ring retainer. Apply grease to the o-ring and slip it over the end of the rod, then put the o-ring retainer on the end and push it down until it's snug against the housing. It's important to note that if your new o-ring is rubber then you should not use a petroleum based grease as they swell rubber, use silicone grease instead. Conversely, if your new o-ring is silicone then use a petroleum based grease instead of silicone.

Reinstall the completed motor and enjoy!

Forum member Inavacuum also posted a good point.
"I did exactly what the thread says to do and mine is working great. I also added a step, I resealed the outer little rubber grommet with some silicone putty stuff to prevent it from happening again."

JF member cyberbonga states that the hatch must be closed before testing the motor otherwise the wiper arm will only sweep halfway.

Last edited by gomes512; 12-10-2009 at 12:51 PM..
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Unread 04-06-2007, 09:32 PM   #3
ajmorell
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Quote:
Originally Posted by gomes512
Okay so I pulled out the rear wiper as I ran across a thread here earlier of someone having a problem with theirs. I figure I'd do it and take some pics along the way. Although having a functional rear wiper isn't necessary... it's annoying in the salty winter roads. Plus this will save you something like 70 bucks.

Turns out the rear motor seizes because water leaks into the shaft of the wiper arm, corroding it. The motor will slow down over time and do one of two things: 1. Burn itself out. 2. Move partly then stop.

I followed the Hayne's manual for instructions on how to remove the motor from rear lift gate.


I carefully removed the circuit board cover by lifting the tabs on the cover with a small knife.


I was greeted with this sight, I pinched the little black button tab in the middle of the circuit board and lifted it up. The board is soldered to the electric motor.


Since I lifted up the circuit board I simply touched the soldered joints with a soldering iron for a few seconds and each contact disconnected itself once the solder was melted.


As you can see, each contact should be free of the motor and the circuit board should be lifted out.


Here is a view of the opposite side of the circuit board. Make sure not to push in the four pins located to the right (they will have grease on them).


Next take a 9/32 bit and unscrew the (4) screws holding the gear cover in place.


You should see something like this. VERY IMPORTANT: Make absolutely sure that you mark the position of the yellow gear in relation to the case. If you don't you will have a headache trying to find the original starting position. The metal brass plate located on the gear is the forward/reverse contact, do not remove it.


Most likely the shaft will be seized in place, use a hammer and hammer the end of it.


Right before you will run out of anything to hammer the gasket retainer will come loose. Save that piece along with the gasket that may or may not come out at this point and continue hammering if need be.
No clicks.
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Unread 04-06-2007, 09:32 PM   #4
ajmorell
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Quote:
Originally Posted by gomes512

The gear will come out in this fashion along with the shaft when you hammer.


Here the gear and shaft have come all the way out (just pull it out). Notice the dark bands on the shaft, that's the problem area. Clean the shaft with carb/choke cleaner or use a metal brush and set it aside.


Corrosion on the shaft also indicates corrosion on the inside of the cone. There should be a small black gasket on the inside end of the cone, save it. Use a metal brush to thoroughly clean the inside of the cone (yes I had a heck of a time pulling that brush in and out of the cone).


Pull out the brush and spray down the inside of the cone with carb/choke cleaner and make sure all metal shavings/dust/dirt have been removed. Roll up some paper towels and pull them through to ensure a clean nothin' but sweet shiny metallic inside.


Using a flathead or knife apply a large wad of grease on the inside of the hole in the cone. Then take the shaft again and lightly cover it in grease and push it all the way through.


Before you push the shaft all the way to the end, ensure that it spins with little friction when it is almost entirely in the cone. This was the whole purpose of the project. Now push the gear all the way down and MAKE SURE IT IS IN THE ORIGINAL POSITION that you marked earlier (didn't you?).


Take the circuit board and lightly apply dielectric grease to the four pins mentioned earlier. DO NOT BEND THEM DOWN or they will no longer make proper contact with the brass plate on the gear.


Lastly apply dielectric grease to the brass plate and the yellow gear to reduce friction/wear as the four pins drag themselves across those parts.

Put the gear cover back on, carefully snap the circuit board back on and touch the motor contacts with a soldering iron again to rebridge the connection and put the circuit board cover back on. Don't forget about the shaft gasket and gasket retainer. Apply grease to the gasket and slip it over the end of the shaft, then put the gasket retainer on the end also and push it down until it is snug against the cone.

Reinstall the completed motor and enjoy!



Just realized I can't actually post pictures directly??? Oh well whatever I tried. Hope this helps somebody.

Once again.
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Unread 04-07-2007, 12:15 AM   #5
gomes512
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Hah, was hoping someone would do that. Thanks a bunch!
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Unread 04-07-2007, 07:17 AM   #6
greasefingers
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Very nice write up. I am sure it will help many. The leaking wiper shaft, from a brittle rubber washer gromet thingy also corrodes the latch/catch mechanism for the tailgate.

Is that red grease, Mobile1 from your grease gun?
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Unread 04-07-2007, 08:17 AM   #7
_Kyle_
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I'm off school this week so i'll have to tear that off and apart one day...
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Unread 04-07-2007, 09:03 AM   #8
madcabbie
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wow, very very nice write up. Dont you just get alot of self satisfaction doing something like that(unless someone else gave you the instructions) I love tearing apart broken things and figuring out how to fix them
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Unread 04-07-2007, 10:05 AM   #9
gomes512
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Why yes it is Mobil 1 grease

Usually when I try to fix things and tear them apart they usually explode and tons of springs go shooting everywhere or things go nice ans smooth.
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Unread 04-07-2007, 07:19 PM   #10
Inavacuum
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I did this today and it worked great!!

No problems except with the little plastic tab things that hold the back panel in place. I broke two of them and the ones I got to replace it weren't exactly very durable. Other than that it went great and I now have a working rear wiper. Also I re-sealed the outer gasket with some silicone puddy type stuff. Over all it took around an hour and it now works great.
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Unread 04-07-2007, 09:04 PM   #11
Vestjam
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Agreed.... very nice write up; however, my shaft was SO LOCKED UP, I split the pot metal shaft housing trying to get it out.

That bit** F***ing hated me!!!

Lets face it... sometimes it's easier to replace than repair
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Unread 04-07-2007, 10:16 PM   #12
gomes512
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actually funny you should mention replace...

earlier today that very unit I tore apart and put back together no longer works. The motor blew out

So much for all my work fixing that pos... oh well.
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Unread 04-09-2007, 02:04 AM   #13
BradBurdett
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my rear wiper goes all the way over then stops, is this a symtom of the corroded wiper motor shaft? If i leave the switch for the rear wiper on and open the rear hatch it will go back to the starting position which i find to be weird but maybe the movement helps to set the corroded shaft free...

any thoughts on that?
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command-trac (NP231) with SYE
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Unread 04-09-2007, 02:04 AM   #14
BradBurdett
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my rear wiper goes all the way over then stops, is this a symtom of the corroded wiper motor shaft? If i leave the switch for the rear wiper on and open the rear hatch it will go back to the starting position which i find to be weird but maybe the movement helps to set the corroded shaft free...

any thoughts on that?
__________________
1995 ZJ 4X4
command-trac (NP231) with SYE
K&N FIPK intake
RE 6.5in lift with 33X12.5 BFG MT and no Rear Sway bar
4.56 gears--axle swap soon
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Unread 04-09-2007, 07:44 AM   #15
Inavacuum
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Quote:
Originally Posted by BradBurdett
my rear wiper goes all the way over then stops, is this a symtom of the corroded wiper motor shaft? If i leave the switch for the rear wiper on and open the rear hatch it will go back to the starting position which i find to be weird but maybe the movement helps to set the corroded shaft free...

any thoughts on that?
If you had read the entire thread, thats exactly what mine was doing. Yes its symptoms of the corroded shaft. I did exactly what the thread says to do and mine is working great. I also added a step, I resealed the outer little rubber grommet with some silicone putty stuff to prevent it from happening again.
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