GP White 928 S4

Car is a 1988 S4 Auto LHD with Positrol (Memory Seat) with 8 way power control (does not have the added lumbar 4-way controls or seat heating options).

When I got the car last year the drivers seat would recline backwards but the switch would not work to move the seat backrest forwards. The rear seat height would go down but not back up. The front switch works correctly and moves the seat in both directions on the tracks.

I ordered a new switch 928 613 201 00 from Roger a few months ago and installed it without issue but it didn't fix the problem. The seat still only moves in 2 of the 4 directions even with the new switch. I also checked solder points on the Positrol memory board and touched up a few that looked suspect. I moved on to other projects in the meantime.

I've also been chasing an electrical drain where the car battery will go dead in 5-6 days if not driven (battery was replaced this year) with no success in finding the source so far. I decided to have my mechanic take a look at it today and he traced the issue to the driver's seat, saying that it has a constant pull detected.

I found this older writeup where the owner was having similar issues with his Positrol seat and resolved the problem by tinkering with the seat relay box: http://www.928s4.com/project/seat.htm The pictures are low resolution and I don't fully understand what he did to resolve the issue with the relays.

Does anyone else have experience with this issue and working on repairing the seat relay box (part appears to be NLA)? If so, can you provide more details or pictures on what you did to resolve it? Also, was this causing an electrical drain that was resolved by cleaning the relays?

I appreciate any help and hoping someone will have the experience if they were in a similar boat.

Ed Scherer

See power seat, mirrors and memory fix.

I think for most people with trouble, the symptoms weren't a power drain, but just problems (often intermittent) with seat or mirror movement (and indicators for the latter).

GP White 928 S4

Thanks Ed. Yeah, it's frustrating because I feel like I've checked most of the pain points in that thread. Added some solder to the Positrol control board where there were a few weak spots. Also, my memory switch lights are working (albeit dim - not sure if that's normal).

My mechanic is suggesting that I position the seat where I want it and then unplug the seat wiring to see if the drain goes away. Not exactly the permanent fix I'm looking for.

Mrmerlin

I would follow the mechanics advice , put the seat where you want it then unplug it,
unless you want to resolder the relay board under the seat

GP White 928 S4

Thanks Stan - I'm honestly ok with digging into the relay board but was hoping someone may have some better pictures or writeup of how to do the process of R&R'ing it.

The Forgotten On

Only thing you can do with that board is to reflow the solder if there are cracked joints and to see if you can de-solder and replace the relays.

The relay coils and contacts have to be a generic size so I'm sure there is a good substitution out there.

Otherwise you can clean the contacts with some emery cloth to get any deposits off.

GP White 928 S4

Had some time finally to dig back into this today. Pulled both seat relay boxes and inspected, no broken solder points or suspect looking boards.

But I also took the cover off the main seat control board and noticed someone has added 3 jumper wires as pictured. What were they trying to accomplish with this? Should I remove?

Mrmerlin

NOTE without a cb wd it would be a guess.
Those almost look factory.
whats on the other side of the board?

GP White 928 S4

The other side of the board is attached to the cover diagram. The jumpered connection is under the "1" section. Curious if anyone else has seen jumpers on their board.

I've also cleaned and added Deoxit to this side of the board where the plugs connect. #2 and 14 are not used with my application.

Mrmerlin

plug one looks like the power relay for the board.
the jumper wires look like they bypass the relay.
still a WD is needed

GP White 928 S4

Finally got closure on this nightmare, with a warm day to tinker today. I was able to confirm my mechanic's test that the seat was my battery draw as I'd left it unplugged for a couple months and had no battery issues since. I did however, want to restore full seat function.

After a few aborted attempts to get into the seat relay boxes I decided to purchase a used Seat Position Control Harness from 928 Intl. Part number 928-612-232-00. Mark saved my bacon as the complex harness is NLA and the used harness worked great! I now have full seat operation in all directions for the first time since I bought the car. Thought I would share if anyone else is in the same boat.