I did this to mine a while back.  I have an 83S so "YMMV" as Ed says.  The base is held on the door by a single allen head bolt that is hidden under the post and revealed when you rotate upper mirror assembly forward.  This should not be a problem as your mirror has come apart anyway.  Undo the bolt (don't drop it).  Turn base upside down.  This will reveal a hollow bolt that the control wires run through.  This is what came loose on you. 
Try to pull a little slack in the cable from the door.  Put towels around the door so you don't scratch the paint.  Flip the base and mirror upside down together as if they were attached normally.  Take a needle nose pliers and grab the lip of the hollow bolt.  Press down and rotate to the right to engage the treads.  Tighten it up.  Flip the mirror upright.  Push the slack in.  Push mirror in forward position.  Reattach base with the allen head bolt.  Flip the mirror back to driving position and you are done.

Hope that helps,
John Eifert
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Mirror upgrade?

Bobarino91@aol.com wrote:
  who has done it?  how long does it take etc etc etc?  will the heated mirrors still work?  thanks in advance for any info.
>

Bobby:
I did this upgrade to my '89S4 last winter. There are several "issues" to be addressed:

1) The individual male and female "pins" that come with the GTS mirror kit motor, will not mate with the S4 style mirror wiring harness. The S4 style pins are much larger and the pin carrier (I use that term out of ignorance of the correct part nomenclature) is flat rather than the round carrier used with the GTS mirror motor pins. My solution was to reuse the S4 mirror motors that had the larger pins and flat pin carrier. The only difference in the mirror motors was the pin size. The alternative is to cut off the old pins from the wiring harness and attach the new smaller pins (which are supplied with the kit) to each wire. This would allow you to use the new style round carriers, but I didn't want to start cutting.

2) To remove the old S4 mirror completely, you need to remove the wiring harness pins from the flat pin carrier. Once the flat pin carrier is removed from the pins, the wiring harness will slide through the mirror mount (still a tight squeeze). This is accomplished with the use of an AMP tool, part # 305183, available from your local electrical supply house, maybe even Radio Shack. The tool enables you to punch out the pins from the carrier. MAKE A DRAWING OF THE COLOR SEQUENCE OF THE WIRES AS THEY ARE REMOVED FROM THE CARRIER.

3) I had the GTS mirror housing and base painted at a shop, then I took the painted parts to my mechanic who fitted the spring between the base and housing (this is the best $20 I ever spent).

The mirrors work as they should and made a dramatic difference in the vehicle's appearance. For me, a worthwhile upgrade. Let me know if you have any further questions.
Regards,
Joe Rausa '89S4
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>2. Any one have experience  upgrading with aftermarket GTS mirrors (repaint & install), if so which ones?

I just took off my original mirrors just to do a repaint of them and I can tell you this, it is a B*TCH!

If you are determined to do this switch and paint, here are the things to watch for and test first if you want to make a purchase decision:

1. The main bolt holding the mirror in place may have frozen.  Move entire mirror body to side and look down into the hole for the alan bolt head 4 or 5mm.  Try it, but don't force.  If it is stuck, you are in for a long job.  This bolt is not very strong and one slip of the wrench strips the head, one twist to hard and the bolt will snap, no kidding.

2. The wires are on a harness and you need to undo each one from the clip in order to slip them through the access hole of the mirror body.  Make very detailed drawings for both sides.  The colors are different for each side!

3. Order up new rubber base plates for the new mirrors.

4. Get some 3M glaze to rid the car door of the mark from the old base plates.  Since the shape is different for the GTS mirrors, (I think), you need to get it perfect.  You might need compound.

5. The internal spring inside the mirror housing, that which it swivels on, is extremely strong and difficult to screw back together.  <--requires two strong people...

6. If you run into problems with the bolt, note that it screw into a barrel inside the door that floats.  It is kept in place by a push pin.  Everything here requires small hands or thin fingers.

7. When threading those wires through, be careful not to damage any of the pin connectors.

If you need more, contact me.

best of luck

86.5 blk.blk 5spd

andreas

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Equivalent for mirrors:

Volvo 93-97 850; 95-96 850 GLE; 95-97 850 GLT; 96-97 850R; 97 850 T-5; 95 850 T-5R; 94-96 850 TURBO; 91-95 940; 91-95 940 TURBO; 92-97 960; 98-04 C70 HT; 98-04 C70 LT; 98-00 S70; 99-00 S70 AWD; 98 S70 GL/ 98-00 S70 GLT; 98-00 S70 T5; 97-98 S90; 98-00 V70; 98-99 V70 AWD; 98 V70 GL; 98-00 V70 GLT; 98-00 V70 R; 98 99 V70 T5; 98-00 V70 X/C AWD; 97-98 V90

Mirror motors and, "the bit that breaks - the toothed rod" are definitely the same, the mounting sub-frame for the motors may well be the same as well.

Jon in NZ