I am continuing the revitalisation of my field find 928 S4. (See previous article https://rennlist.com/forums/928-foru...l#post20351412).
As the S4 is now driving quite well, it is time to address the boring items that make it a car, such as lights, wipers, and other ancillaries. I found that the wiper motor was completely dead. Putting power directly to the wiper motor pins yielded nothing, not even a slight noise or attempt to move the wipers.
I was astounded to find out that the cost of a new wiper motor is $700. It was time to get creative and find a more economical alternative. Searching the 944 forums (https://rennlist.com/forums/924-931-...-996-part.html) , I discovered that someone has successfully installed a wiper motor from a 986 Boxster into a 944. Given that the late 944 uses the same wiper motor as the 928 S4, I decided to pursue this idea. I found the pinout of the Boxster motor from the Rennlist post, and used a factory diagram to find the pinout of the original motor. There is a conversion harness available for sale, but I decided to get creative and make my own. I sourced a wiper motor pigtail from a 944 and a used 986 Boxster wiper motor. Unlike the thread mentioned above, I did not have to make any modifications to the mechanical components of the linkage.

Replacing the wiper motor was quite simple. I removed the intensive washer reservoir bolt and moved the reservoir out of the way. I then marked the position of the wipers on the windshield with some masking tape, as well as marked the wiper motor arm position relative to the linkage assembly. I loosened the only two accessible wiper motor bolts (10mm) and the wiper motor drive nut (13mm). The wiper linkage arm came off without a fight, surrendering to slight upward pressure from a flathead screwdriver. I removed the motor ground as well. I then moved the wiper linkage out of the way to access the third 10mm bolt holding the wiper motor in. Rotating the wiper motor to clear the drive end allowed the motor to come out without disturbing the linkage assembly. I then installed the Boxster wiper motor, which is noticeably smaller than the original. I then activated the wipers to properly orient the wiper motor, and installed the linkage to the motor in the same position as it was before. Testing the wipers after connecting linkage revealed that the transplant was successful!




Having the wiper motor out gave the perfect opportunity to vacuum out the accumulated leaves in the cowl. A new cowl cover is needed.

The only slight drawback of this modification is that the Boxster wiper motor is only 2 speed, as opposed to the original, which is 3 speed. However, the Boxster part moves the wipers effortlessly, and it is a readily available part, that is also reasonably priced.

If anyone else is interested in doing this conversion, please see below pinout of the 928 pigtail:





And the Boxster pigtail:

From top to bottom:

Brown

Yellow

Blue

Red

Green



I hope this thread provides others with a viable solution for inoperable windshield wiper systems. While I do not plan to introduce my S4 to rain, this gives me confidence to use the car for longer journeys.

Cheers,
Michael

 

Thanks for sharing Michael.
I will print and add to my files