PC-85-928S

My rear wiper always worked great.
Recently when I press the button, it goes to the right but does not return.
I replaced the transmission assuming the white plastic **** had worn down and it was popping out of the bracket mounted to the trunk area.

This did not fix it.

I grinded the lip on the trunk area, trying to make it a deeper grove-
This did not work.

I think it is popping off the trunk bracket, because the lip is worn, or the hatch is not closing flush enough.

I don't see how to adjust the hatch for a tighter seal.

jpitman2

Screw the rubber snubs on the rear corners of the hatch in a bit, it should close a little tighter. Does it appear to latch correctly now - ie you cant pull it up without using the key? It might be the self park circuit in the motor has failed. Not sure in this case, but many such circuits depend on a good earth.
With the hatch open press the wiper switch, and see if the fitting in the trunk goes back and forth, or just one way from parked. It it goes back and forth, the problem is engagement with the arm outside; if it goes only one part of the wipe, its inside the motor.
jp 83 Euro S AT 55k

MainePorsche

I had the same problem.
This may sound elementary, but make sure BOTH nuts are adequately tightened under the wing.

PC-85-928S

Did the rubber nut thing & it does turn with hatch open.

Ducman82

mine will do that as well from time to time. so i just dont drive in the rain... LOL

Jim M.

Mine works just the way I want.

Sorry, that's all the help I can offer.

ThetaTau87

This is what I'd like to do. Are those plugs a Porsche part? Part number?

brealytrent

Have you ever seen a stock 928 without a rear wiper? No? Then I'd say NO.

Jim M.

Nope, home made electric box plugs from Home Depot. Removed two tabs 180 degrees apart then bent it in a notched piece of wood. A little paint and sealed in place with clear RTV to make it waterproof. Took maybe an hour to do, plus waiting for the paint to dry.

Mrmerlin

before you throw in the towel ,
loosen the mounting bolts of the actuator bracket and slide it upwards, then tighten the bolts,
try lubricating the pivot arm shaft so it slides easily up and down,
this will then let the lower drive arm be free to stay engaged
NOTE this is part of how the engagement arm works.

the other thing to do is lubricate the wiper arm pivots and possibly bend the arm down so there is more of a latching going on..

make sure your female collar in the hatch latch is in good condition,
and that the rubber bumpers and hatch side bumpers are correctly adjusted.
NOTE the ends of the hatch should be flush with the corners of the chassis

Barry Chan

Yes, mine was like that, one wipe and it stayed on the right side of the hatch window, i lubricated the arm shaft and it worked ever since, hope yours is as simple.

PC-85-928S

I heated up the wiper transmission arm, so I could try and bend it, to give more grab.
The heat caused the small white plastic mini hockey puck thing to pop out.
It seems to me, if I could find a larger piece of plastic to fit at the end, it could provide the extra distance to engage the mechanism in the hatch area, and not pop out.

928cs

The rear wiper was an option for early 928, and CS too. But in this case, there was no holes at all.

Removing it was the first thing I have done to my "new "S4. I'm used not to have one with my former CS.

Bill Ball

As the rear latch tongue wears, a rattle will develop from looseness in that area. So, people end up screwing the rubber bumpers on the corners of the hatch out further to take up this play and reduce the rattle. This raises the hatch above the quarter panel line, and the stalk on the upper part of the wiper mechanism no longer fully engages the hole in the bottom plate. Also, if the stalk, which is rather soft metal, wears unevenly, it will eventually fail to engage, even if the hatch is not elevated much by the bumpers.

So, first make sure the hatch is not elevated above the rear quarter panel edge - this should be flush. Turning in the rubber bumpers, as other recommended, will bring the hatch lower. If a rattle develops, then you know the upper latch tongue needs replacement. Alternatively, sometimes there is a spacer plate below the lower hatch latch receiver flange that can be removed to bring everything down.

If none of this applies or fails to fix the rear wiper operation, then look at the stalk on the upper wiper mechanism. I found that the soft metal was worn down quite a bit when my wiper began to act erratically, like yours. I found a small steel cap that was just the right size and epoxied it over the stalk (see pic). That was years ago. It has worked fine since. Not sure where I got the cap. I had thought about drilling the stalk an using some kind of screw to build up the height as well, but the cap was a simple solution.

brealytrent

Perhaps, for those of us who currently do not have this issue but want to prevent it from happening, we should also apply a dry lubricant such as graphite powder?