V70 rear wiper issues + solution

[R-P]

Hi all,

Since I spend a lot of work on the rear wiper, and I didn't find a sticky on it, I thought I'd post this, as it is quite different from the one in the 850 forum.

It is a write-up that I posted on another forum, so please forgive the copy-paste action and let me know if something has to be changed. I will try to make it into a coherent posting...

Original problem description:
My V70 '04 's rear wiper doesn't work anymore. It only makes a ticking noise (sounds like a relay) coming from INSIDE the motor/gearsystem of the wiper. I think this is trying to switch it on to get it to return to the 'zero'position, which it is not atm.

It had issues before I think (it would stop at 2/3rds from left to right, then continue a second later and go to 1/3rd from right to left), but now it has failed completely.

Checked the hinge cabling mentioned as a possible culprit, but that is in pristine shape. Fuses are all OK.

The whole unit of my '04 model. Getting it out is straight forward and I don't have any pics on it (4 torx screws will take the bootlid-doorcard off (pull off gently as there are still pins keeping it attached to the bootlid), three 10mm bolts fix the motor, take off the washer-tube (gently wiggle while pulling), take off the wiper (flick the hinged plastic part up to reveal the 13mm bolt which you undo, wiggle the wiper (use the 'arm' of the wiper to exert force) to get it to slide off) and pull out the total motor assembly gently).


Issue in getting it disassembled: turns out you can carefully pull the spray-nozzle (the actual jets that spray on the window, 1" piece of plastic) out, and this means you can pull the entire water-tube out of the axle (beware of the tiny o-ring that closes this inner-tube of brass (? at least brass colored) from the rest of the axle!!!))



Both sides of the PCB. Clearly visible is a Diode (black round electronic component that will only pass current one way, so will stop any current from flowing through the motor if someone would apply the 12V the wrong way around) and the thermal fuse (silver rectangle next to the diode) that makes the infamous ticking noise by switching off when too much current is passing through it (and automatically restoring itself once cooled off).
Also visible is three contacts for the positioning circuitry (see pictures of backside white toothed wheel, this is where they attach) and two contacts for driving the motor.





White toothed wheel that is driven by the motor and turns a round motion into a back-and-forth-swinging-motion. Note the backside that features a simple system to 'tell' the assembly in which position the arm is. It's a very dumb system, it will supply current or not (probably to the interval-relais through the yellow wire), depending on whether the middle contact-sleeve is making a short to either the outside or the inner one. I heard a mention about the resting position of the arm not being the same: this makes it very plausible: the friction of the wiper to the window combined with the inertia of the whole system will determine the end-position. Not saying it is a bad system, but it is crude. And therefor simple, and therefor durable. But not nearly durable enough, or this thread wouldn't exist...


The three contacts that interface with the rear of the white toothed wheel.


A separate part that came out ofter thoroughly cleaning the o-ring groove: turns out this part makes up the o-ring groove (along with the entire housing of the assembly). Possibly I have tapped it in too hard, causing the o-ring to have too little room to properly settle, so as soon as I find a replacement o-ring, I will be taking this part out again, and next time will be mounting it with less force.


The actual o-ring (pardon the lousy quality of the pic... The measurements were 1.4mm thick and 12mm outside diameter, IIRC!!!!! Will try to get a replacement at work and will mention which size works best If I ever find out.





Couple of pics of the metal gears and the thing I always refer to as the "axle" (I hammered this out of the plastic housing: not the best of ideas, as I damaged the top a little):


Note the spring loaded ring on the pin that slides into the white toothed wheel:


Magnetic, so pulling it loose will feel like you're pulling apart some wiring... Also notice the bent tabs. If there is no need to take the motor apart: then DON'T!!!!! You will always damage the plastic that the tabs hook on to, so after doing this a few times, the plastic will be severely damaged!

The motor insides:

Also note the spring-ring and tab lying on the newspaper. Don't forget this when reassembling it (yes, I did forget... and had to bent the tabs loose for the second time...).
What this does exactly is not quite clear to me: the tab moves outward once the wiper arm changes direction and the spring-ring keeps it from falling out (this means the bulk of the motor actually moves 1/8th of an inch as well I think). So even though the white toothed wheel goes round and round, something in the motor shifts during this reversal of wiper-arm direction. Possibly this is build in the absorb the direction change and the accompanying forces. The wiper arm goes back and forth, the white toothed wheel turns around, and the part of the motor also moves back and forth..... ????? It has to do with the first part of the movement: the motor is "pushing", the second part, it is "pulling".
Just a wild guess...



Here's some extra info:

And the plot thickens...


After doing all the work mentioned above, it still didn't work, and I thought it may have something to do with the o-ring being old, or the axle unround.

So I got it out for the third time and did some measuring.
The motor used 3 ampere and the voltage at my powersupply dropped to 8 or 9 volts (it is a 3A powersupply). I then reopened the box that contains the PCB and rang the manufacturer of the current limiting switch. It does not have type-number markings on it, but they confirmed my thoughts that this may be on the bottom. So after desoldering the unit, I gave them the numbers and they gave me the specsheet. Which they would not let me place here.

But the essence is that it trips at 7.2 A within 4-10 seconds. Testing showed this was about right, and further testing showed it tripped at 3A after 2 minutes. Since my motor uses 3A@8 volts, it will simply never work, so I deduced the motor has to be faulty.

I did a quick test with two powersupplies paralleled and the motor (without the currentswitch in place) now used 3+3=6A at ~12V. And this was without any gears attached!!!!!
So I opened up the motor. Again. And as said last time: you have to fold away metal tabs and you can only do this so often, as they damage the plastic housing.

I tried to reassemble it away from the gearhousing so I could turn it to feel the friction, but this didn't work well for two reasons: (1) the upper bearing is fixed in the gearhousing (and without it the magnetic force pulls the two motorparts together, so you cannot determine if it runs freely), and (2) the axle of the motor wouldn't go through the bottom bearing.

So I also removed the lower part of the motor housing (once again: tabs, even worse ones than the ones holding the motor attached to the gearhousing...). The bottom bearing was misaligned. After thoroughly rotating, lubricating and fiddling, it seemed quite smooth again.

I reassembled the bottompart, attached the motor to the gearhousing, whacked all tabs into place and hooked the motor up: succes: currentdraw at 14V: 0.7A. About 10 times less (!) than half an hour earlier.
Resoldered the current-limiting-switch, and after hooking everything up in the car, I now actually have a working rear-wiper [thumbup]

So to recap:
My problem was the axle running from the gears to the wiper.
When fixing this I may have added a new problem, or may have overlooked an existing (possibly bigger) problem: the bearings of the motor.

Two pics of the top-bearing. Not sure whether the axle is supposed to rotate inside the shaft or that the 'ball-jointed' bearing is supposed to rotate within its outer part as well. The fact that it is somewhat of a ball-joint (?) was the reason it was misaligned at the bottom of the motorhousing, and I couldn't get the inner-part of the motor to slide in. That's what forced me to open up the bottom part, of which I obviously have no pics, as I got carried away and forgot all about pictures. Both bearings, top and bottom, seem identical.

And at a slight angle


The thermal current limiting switch. The 24V3T marking is NOT a 24 volts 3 ampere slow-tripping marking, but a date Week 24 in year 03 probably. The "T" is the plant where it was made.



Two more pics of the motor. Take note of the V-shaped tabs on the left side of the pic holding the plastic bottom part attached to the metal middle-housing... Pita to open (vice works well) and close (hammered a pin inbetween to wedge them apart again, but you cannot put the metal middle housing into a vice while doing this, as you may deform it and screw up the entire motor...)



Hope this helps you lot, as this seems a pretty common problem. I have heard people getting good results from simply drowning the thing in WD40, but where's the fun in that...