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Thread: Trying to diagnose rear wiper troubles

  1. #1
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    Trying to diagnose rear wiper troubles

    A few weeks ago, my rear wiper stopped working at the top of its arc on my way to the mountains. On my drive back home, I turned the wiper back on and it went back down, then up and stopped again at the top of the arc. Since then, no matter what I do, it won't budge.

    Today, I tried flexing the wires inside the flexi-conduit between the body and the tailgate, but it has no effect. I removed the conduit and felt the wires inside, and I couldn't feel anything apparent. The wires were wrapped in electrical tape though, so I didn't have access to the wires themselves. I checked the fuses, and they seemed fine.

    I just checked with a multimeter, and I am getting power at the motor. 2 of the terminals showing 31v, the other none. I noticed when I bridged the ground wire to the tailgate housing, I hear a click in the motor, (I'm guessing a relay), but the motor isn't turning, nor making any sounds to indicate it's trying to. So, I'm not sure if that is an indication of a ground problem, or a crapped out motor. Tomorrow when it's light out, I'll try removing the motor from the tailgate and see if I can figure it out.

    Open to any thoughts in the meantime.
    Last edited by thepuzzlemaster; 04-12-2021 at 12:26 AM.

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    Re: Trying to diagnose rear wiper troubles

    Okay, did a bit more investigation last night. Upon closer inspection, I'm definitely getting power to the motor, so the cables are good. I opened the motor up (The actual motor is quite beautiful!) and no worn teeth on the gears. I ran the motor with the backplate off, and the motor turns about a quarter turn and then binds up. Rinse and repeat - no movement.

    I'm thinking the other end of the system (the arm which the wiper blade attaches to) likely seized up, so it's preventing the motor from spinning. It's a very greasy mess in there, but I have a feeling I'm going to have to take it apart and see if I can free it up. Or, find out there's something else going on I'm not aware of that's causing the problems.

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    Re: Trying to diagnose rear wiper troubles

    Not sure how similar your van is compared to the NA model, but maybe check this thread Rear wiper motor problems!

    Carbonized provided pictures that may well help. (post #15)

    You will need to check the integrity of the linkage arm and the transmission (the tower that the wiper arm bolts on to)

    You have verified that the wiper arm is tight on the tower, yes?
    They do have a habit of working loose, sometimes.





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    Re: Trying to diagnose rear wiper troubles

    Thanks for the thoughts. That thread has definitely been really helpful. It's what lead me to check the wires in the conduit, and ultimately made me realize I had been testing the terminals incorrectly with my multimeter.

    That first photo of the motor housing is pretty similar to my van, but a little bit different. But I'm honestly not sure what that second photo is. It looks to be part of the tailgate locking mechanism moreso than anything related to the wiper. Or at least, there's nothing like that in my van, that I can see - related to the wiper. I'm not sure what ball-joints they're referring to either.

    I tested the motor with the wiper arm completely removed, and with the motor back completely open exposing the inner plastic gears, so I'm 100% confident the gears are binding (although not 100% sure on what), and it's not a slippage issue or a worn teeth issue. I tried turning the motor manually with the housing off, but I don't want to snap off any teeth if it is in fact seized up. And I'm not sure how much pressure it should take to turn this thing, so I don't know how much "muscle" to apply. I'm assuming the motor itself is not terribly powerful, or else I would have expected the teeth to have already snapped off. So I'm being a bit gentle with it. It's also just a relatively small motor - so probably not very powerful in that regard either.

    FWIW, I just had the motor in my van messing with it, and that thing is loaded with grease, so I didn't want to make too big of a mess in there, so I wasn't able to really get in there. I'm going to take it out to my workbench later and see if that helps me get to the bottom of it. Appreciate all the thoughts. I'll post some photos when I've got this thing all taken apart.

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    Re: Trying to diagnose rear wiper troubles

    I have a rear hatch door that came off a JDM van, but an earlier version no doubt.

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    The motor assembly bolts to the door, and is comprised of 2 subassemblies, the electrical side with the motor and the gearbox side with the grease.
    Mechanical faults to that part of the system are relatively rare and most of the trouble is usually "downstream".

    Behind that gearbox you had apart, there should be a crank arm with a push rod attached, the push rod goes to the wiper pivot.
    The push rod is attached to the motor and the pivot with "ball joints", white plastic retainers that snap over the ball of the drive
    Those plastic caps have been known to fail and cause trouble

    The wiper pivot itself is the most troublesome part of the system.
    Its exposed to the elements, is made of dissimilar metals and mostly gets ignored.

    You will need to inspect each part to know where the fault is.

    Only other thing I would say is to disconnect the wiring at the motor and use a battery to power it for testing purposes, thereby eliminating the switch/wiring from the circuit.
    I once chased a wiper problem for far too long before realizing the fault was actually in the "intermittent" part of the switch.
    I was testing the circuit using the switch, cause it was faster than taking it all apart to get to the connections.
    Once I powered up off 12v battery, the fault disappeared, doh!

    Probably not your issue, I only mention because I have learned to eliminate as many variables as possible, when diagnosing faults.
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    Re: Trying to diagnose rear wiper troubles

    Well, I took the motor apart and tried to get things moving again, but couldn't get it to function. I ran some penetrant down the spindle arm to try to loosen things up in there. But I couldn't remove the clevis pins to actually get the gearing out. I haven't given up entirely on this, but I'd definitely consider a replacement if I come across one, rather than trying to repair this one.





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    Re: Trying to diagnose rear wiper troubles

    So, if I understand correctly, with everything in place and the cover off the motor, it runs for a bit, then stalls and wont "restart", yes?
    If so, is this your basis for flagging the motor as the failure point?

    Is its anything like the door from the pictures I posted of a JDM rear door?
    Is there not a link rod between the motor and the wiper pivot? (it would attach to the motor on the BACKSIDE of the gearbox)
    Or is the wiper pivot a built-in part the motor housing itself?
    Maybe post pictures of what your into?

    Generally speaking, one would diagnose a "seized" wiper problem (front or rear) by popping the link rod off the motor and manually articulating the link/wiper assembly to verify pivot integrity.
    The motor would be tested by disconnecting it from the vehicle harness and powering up with 12V direct (with the link rod disconnected) to verify function.

    Kinda sounds like the whole system is in play and your flagging the motor without isolating the various elements, that can get expensive, if you're wrong.

    Wiring, pivots, linkages and switches (often in that order) are the usual suspects.
    Motors, not so much.

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    Re: Trying to diagnose rear wiper troubles

    I didn't mean to imply that the motor itself was bad. I think the motor actually runs fine. I think it's seized up because when I turn the motor manually, I'm met with a lot of resistance. I don't want to force it because I'm worried I'll start snapping teeth off the gears.

    I did put the wiper arm back on the spindle and attempted to to force it to rotate while also manually turning the motor, and it did actually start turning a little bit from doing that. I tried installing it all back in the vehicle thinking maybe that had broken whatever was holding it tight, but it still showed the same symptom where it would attempt to turn, but bind, click, then pause. Rinse and repeat. I'm thinking the motor is trying to turn, but binding and triggering some sort of waiting period before it attempts to spin again.


    I might try removing the motor again and putting more penetrant down between the spindle and its housing and then manually turning the motor more while forcing the wiper arm to rotate to see if that might help free it.

    It definitely might be something else entirely as well.
    I also might buy a pair of snap ring pliers so I could hopefully take more of the assembly apart and try to really clean things out.





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