Windshield Wiper Motor Malfunction

Unfortunately, my rear wiper on my Audi 80 Avant has been malfunctioning for some time. It works fine in continuous mode (when I use the wash-wipe function), but not in intermittent mode (by briefly pushing the stalk lever backward). The motor is fine (it has been replaced), and I even tried replacing the interval relay as a test, but there's no improvement. The wiper still only makes a short movement – about two-thirds of the 'total distance' – and then stops, only to move about two-thirds across the windshield again after the next activation by the relay. So, it doesn't reach the end, and it also doesn't stay in the end position.
What could that be? Is there still a control unit in the steering column that determines the duration of the pulse?

Hi,

I suspect there is a feedback line that informs the control electronics when the end position is reached.
Could it be that this line is disconnected?
I suspect the function works as follows: When activated, a time-limited pulse is sent to the motor. This time limit is presumably to prevent the motor from burning out, for example, if the wiper is frozen. The wiper then starts moving, and a control line signals that the end position has been reached. If this line or the sensor is not working, the end position may be continuously reported, and the motor will stop after the initial pulse duration.
If the motor (with its sensor contact) and the electronics can be ruled out, I would still suspect a broken wire or a short circuit (depending on the function) in the feedback line.

Regards,

Eike.

Hello Eike!

First of all, thank you for the information... I hadn't even considered such a type of controller initially...
To perform the test: Would it be sufficient to simply bridge the wires from the relay (2/53 and 8/53a) to the motor? I would probably exclude the wire from the motor to ground (31), since the motor runs when it does run (meaning there's always voltage there...). According to your explanation, the wires from the switch to the relay should also not be relevant, correct?

hello
Have you checked the cables in the hinge area of the tailgate? The sound suggests that the cable for the end-of-travel switch might be broken.
gerrit

No, I haven't checked it yet.
I was thinking something similar, but as I said, I thought it was unlikely that there would be a separate positioning device in the motor.
First of all, thank you for your help. I'll try to tackle the problem this weekend.