Swapping rear view mirrors

The auto dim rear view mirror in my '98 GS developed spots & cracked so I'm swapping it for one out of another GM vehicle. This one has map lights and manual dimming.
The auto dimmer unit cable has five wires and the replacement has only three.
Anybody know offhand how to select the right three wires to splice the first time?
Thanks in advance.

Sounds like you will need to reference the GM FSM wiring diagrams just to be sure. Since the replacement rear view mirror just needs 12 volts and a ground for the two map lights just find the wires that provide those signals. Trial and error and the most that could happen is possibly a blown fuse. Good luck!

For 2000 regal, wiring should be same as 98, mirror with map lights only and
without auto dimming: orange for 12v (C terminal), Black for Ground (B),
and white for ground (A terminal). Terminal D is not used.

However, with auto dimming, 2000 lists 7 wires with pin number:
1 brown Fused voltage
2 black ground
3 lite brown back up lamp feed
4 gray auto dim signal
5 pink auto dim return
6 white map lights
7 orange 12 v from electronic control unit.
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