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A while ago, I had a Durametric scan on my 996 (1999), and during the Short Test I received fault codes 22 (Potentiometer right mirror Open circuit vertical) and 20 (Potentiometer right mirror Open circuit horizontal) under the Seat Memory section.


My question is, where are these potentiometers, if I wish to inspect them for either being worn out or having a bad connection? I can manually adjust the passenger mirror with the mirror controls, it's just that the passenger mirror doesn't work with seat memory. I'm taking a guess that the mirrors only have motors in them and these potentiometers are probably in the modules under the seat or in the door sill, but I'm not sure which, and where specifically. Also, are these potentiometers tiny little trim pots on a circuit board, or some kind of larger specialized potentiometer component with a part number? Or does one typically replace a larger module for a fault like this?


The closest thread I could find on the subject was this one: http://www.renntech.org/forums/topic/40724-seat-memory-function-issue/?hl=%2Bmirror+%2Bpotentiometer - but it appears his issue was fixed by plugging something back into a control module that was intentionally unplugged, and did not reference the specific potentiometers.


Any more specifics or even links to circuit/wiring diagrams for this area would be great. Thanks in advance.

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  • 3 weeks later...

Follow up (if anyone was curious):


I was wrong to assume the potentiometers would be trim pots or something on a circuit board somewhere (I'm too used to thinking of circuitry in terms of amplifiers and such, I guess) and not in the mirrors themselves. They ARE in the mirrors; they're attached to the electric motors in the mirror motor part. This actually makes a lot of sense, because it's how the mirror can remember it's positions by the motors actually physically moving rotary potentiometers and then remembering the resistance of that position. I should have thought harder about why they would need a potentiometer instead of a fixed resistor (since it is not a user controllable potentiometer).


One option right now is to buy a mirror motor (or more likely, since I prefer to be frugal when I can, strip a used mirror for the part), since the potentiometers are kind of assembled attached to the motors and don't really look reasonable to disassemble and rebuild. However, I find it peculiar that both potentiometers in the same mirror have failed, but both of the motors are still working perfectly, it didn't seem too dirty inside (the gears on the motors/potentiometers are spotless clean and free of obstruction). I think it might be a communication issue to/from the potentiometers, so I may end up taking the seat and/or sill out anyway, and checking connections (connection at the mirror seemed solid).


Related Question: Looking under the seat (without taking it out), I see a couple zip ties on some cabling. I'm not the original owner - is that a sign that someone has already been working under there before me, or does Porsche use some zip ties on certain cabling runs? If someone has done some work in there, here's hoping it's as simple as forgetting to plug back in a couple wires firmly.

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  • 2 weeks later...

Hey JTT - I'm jealous you're living in Halifax. My wife and I keep saying we need to win the lottery so we can retire early and live in Lunenburg.


More of an update:


I decided to be lazy, and rather than taking the seat and sill out and checking the modules first, I picked up a second hand mirror for $40 to swap the guts out and then at least I'd rule out the potentiometers, if it didn't fix it. About 8 hours after I had ordered the mirror, hindsight kicked in, and I realized I could have just tested with my working mirror on the other side by swapping parts - to potentially save myself the $40. To add insult to that injury, when I opened up the "new" mirror and went to take the motor out, I realized the plug going into the motor only had 3 conductors, and mine has 8. So that wasn't going to work anyway. I guess I also should have done more research on different mirror versions for the 996 - I wasn't aware there were any. On a side note, would anyone like to buy a red driverside mirror with a 3 conductor motor and glass in it? Maybe it's the Boxster version? I'm not sure.


I still needed to definitely rule the mirror motor/potentiometers out. So first I opened up the motor a little more and inspected the circuit board - it all checked out ok. So I ripped apart my other (working) mirror and swapped the motor to the non-working mirror. The same mirror is still lacking memory functionality. As my gut was telling me, my problem definitely not the actual potentiometers on the mirror motor. My problem must either in the wiring, or the controls on the door sill, or in the module seat.


So my next step will be to probably check the sill and look for problematic connections or circuit board components in there. Maybe water damage from wet feet dragging over the buttons or door left open in the rain? However, it may take me a while to get to that point, as my time is at a premium lately between a work project and a newborn. Additionally, I have other jobs on the car that are higher priority than the mirror memory. If the sill buttons check out ok, then I will look under the seat, but I might put that job off for a while, because I actually want to replace my seat belt buckle down the road, and it'd make sense to do those jobs at once.


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Lunenburg is a nice little town for sure.  I think I'd like Texas better in Feb though :cold:


When you say door sill controls, you mean the memory buttons on the driver side correct?  I hadn't really thought about them.


I haven't touched mine, been swamped with work and building a new garage.  I appreciate you keeping me up to date!  I'm horrible at diagnosing electronics.

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  • 6 months later...

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