A strange mirror problem on an '88.
 

I have an '88 Targa that's been sitting for 15 years. I bought it and have been working on it for a while. One strange problem that is has is the mirrors operation.

Basically the switch on the door works like this - right mirror goes all directions properly - right/left and up/down. Left mirror only goes right/left. I tried cleaning the old switch and left mirror started working fine. But then after I took the key out of ignition, put it back in and tried again the same issue came back. So I replaced the switch. Worked fine until I removed the key. I figured maybe it's a contact somewhere. So I took the new switch out, lubed all 5 pins with dielectric grease and sprayed the connector with contact cleaner. Same result, worked fine until I removed the key.

Any ideas? I'm stumped but thinking maybe relay or something?

I am inclined to say it may be associated with the changeover switch (contacts or connections). If the right mirror consistently functions correctly, the door switch cannot be the source of the problem as the same set of contacts are used for both mirrors.

It is also possible that there is a bad connection in the harness to the left hand mirror.

I really cant make any sense on the ignition off/on behavior. I'll think on it and let you know if I come up with anything though.

Sounds good! Thank you.

Was the switch gunked up or just contact corroded ?

This is on my list.

Couldn't find anything specific. I just did it to rule it out.

Mine does the same thing, commenting to follow

You need to monitor the up/down 12V power with key on/off on the left mirror. If the 12V power is always there,
then the up/down motor is intermittent.

I’ve had some experience with the mirrors on my 87 Targa. My first step would be check all those fragile connectors in the wiring harness. They are super fussy. You need a pin tool to release the individual connectors. Have they been worked on before you? Could be wired incorrectly.

Which connectors are you talking about specifically? I cleaned the ones that go to the mirror switch itself so I don't think they're the issue.

Update. I tested the rocker switch under the dash. It was fine, continuity perfect on all pins. So it's something else.

Do you have the Bentley manual? Wiring diagram might help.
Since you have an 88, the mirrors and switches are those specific to years 86-89. Wiring diagram on page 970-92 of Bentley manual. Mirrors of this generation have only one motor and an electromagnetic mechanism that switches between up/down and right/left. Joystick is specific to those years and has six pins.

Older mirrors had two separate motors, one for up/down and one for right/left, and no such electromagnetic mechanism. Joystick for this older version was specific and had only five pins. Wiring diagram on page 970-91.

You mentioned cleaning the joystick five pins, so I suspect you might have an older mirror system installed by a PO, or at least the wrong switch for your mirror system.

Also you said you replaced the joystick and the issue came back, so that probably means the joystick is not the cause, except that it may not match your mirror system.

You first need to check if you have 1-motor mirrors or 2-motor mirrors, and this on both sides.

As a last test, you could try to reproduce the issue with the ignition key on/off for the right hand mirror?
Try this: Switch the change-over switch (rocker switch under dash) to the right and leave it on this position. Switch on ignition and exercise up/down and left/right motions on right mirror to make sure all directions are functional. Leave the change-over switch to the right and switch off ignition, then switch it back on and see if right mirror is still fully functional in all four directions or now shows same up/down failure as left mirror. If right mirror still moves in all directions, then the problem is probably internal to left mirror.
Or you have some sort of hybrid mirror system, i.e. a mixture of mirror generations and joystick that do not match and are not stock.

It seems that for some reason power (12V) is applied permanently to left mirror electromagnetic mechanism as long as ignition is on. This is what would cause it to stay in left/right mode. Only when the ignition is cut off can power be removed and so the mechanism is released, allowing up/down motions when ignition is switched back on. Or this is the other way around.
These are just ideas, nothing sure. Hope some of them can be checked to help diagnose this issue. Good luck!

A friend of mine has original Porsche manuals for that year. I'll see if I can bug him to let me look at them.

The car has 65K original miles and only 2 owners. The harness looked fully stock and untouched along with the switch itself. I seriously doubt someone replaced the entire thing although anything's possible.

I'll try the test soon and report back. Thanks for the info, this is good stuff!