Eltel wrote:
If the wires connect directly onto the mirror glass itself then I would say its a heated mirror, and it would be more than likely activated when you press the button for the rear de mister , I could be wrong but that's generally how it works.im new to Porsches myself so somebody else may be able to confirm this
Yep, that is how it works - if you look at the diagram I supplied you can see the heater element connected to pins 5 and 6 - a brown (ground) and a brown/yellow wire. A white and white/brown pair go to one motor and a black/brown goes to the other motor. A link wire should go to this other motor and connect to the white/brown.
It is difficult to tell the colours of the two sets of wires in the photo, so I can't suggest anything further apart from taking the glass off - easy with a screwdriver in the hole underneath (see clarks garage for explanation -
http://www.clarks-garage.com/shop-manual/body-10.htm) there is a rotating locking ring assembly. Unscrew the motor plate and see where the various wires go in both mirrors. It could be that the link wire has been made there rather than at the plug, so that might account for there only being 5 wires. However, a visual inspection will reveal all...

It is possible (as your car is an 86) that your original mirrors are the older style and the replacement is the later. I cannot find any mirror wiring diagram for the older style in the 944 workshop diagrams - they seem to be completely missing - so I cannot confirm the earlier wiring. Are the bases to the mirrors the same shape/profile? I think these changed for the later versions and a hole is provided to access the locking ring - otherwise they do look similar.
Like I suggested, I think the best course of action here is to take them carefully apart and inspect and compare - the situation should become clearer then.
