This is the mirrors wiring diagram - it was so easy in the old days with manual adjustment!
I have added a small voltmeter on the dash running off the wiring to the mirror switch as there is no warning light when the alternator fails.
Removing the glass from the rear view mirrors.
With ignition on move side mirrors to the most inward position - there will now be a gap at the outer edge were you can insert a long thin flat screwdriver. Look for the circular plastic ring, there will be a plastic tab facing away from the mirror on the ring at 90 degrees to the ring. Put flat of screwdriver at edge of tab and gently pry/clip it off.
Refit by gently pressing it back in.
this became necessary after the left side mirror was hit by a sticking out tree branch at 30mph (yes it did, the tree jumped out at me). Although it still worked (and the glass didn't break despite dangling from the heater wires) the assembly needed replacing.
there are two connectors to the mirror - unclip by pressing both sides in (double-clipped and extremely fiddly).
break the securing clips off so it can't happen again
the black connector has 3 wires for the mirror movements - one is hiding! The brown connector on the powerfold mirrors has 4 wires as shown (the standard non-powerfold mirror has just 2).
The mirrors are secured by a single long torx bolt (accessed from under after folding the mirrors fully in) . . . . . .
It would have been better to have removed the cobwebs first.
the long bolt screwed into a plastic piece located in a hole in this support. The plastic broke when I removed the screw (possibly damaged in the impact).
so I inserted and Araldited (belt and braces) a rivnut (blind nut) and bought a 100mm long M6 button-head screw.
to retrieve the top cover from the old mirror, I first removed the mirror (see above) from the assembly.
then I could see the underside of the clips that held the yellow cover tightly in place. These are not very strong so a bit of careful poking with a small screwdriver unclipped them.
the cover then clipped in place on the new mirror body.
Then fitted the new mirror assembly. Retraction worked fine BUT the mirror wouldmn't adjust in either direction. Off again and checked the wires on the bench - none broken but the mirror still wouldn't move. Replaced the mirror pivoting assembly with the one from the old mirror - worked perfectly. With all the too-ing and fro-ing - it had been a good move to break the securing clips!
Problem was - not wiring, but BOTH motors in the pivoting assembly were seized solid - the new mirror was genuinely unused - but had been badly stored!