Early autodimming mirrors used an electric motor to physically move the mirror up and down to control glare. Recently autodimming mirrors have switched over to using electrochromatics which has no moving parts. There are two big manufacturers of EC mirrors: Gentex and Donnelly
I chose a gentex autodimmming rearview mirror with compass and thermometer for my 98' crown victoria police interceptor.
Catch a 12volt positive lead that was hot with the ignition turned to the on position
Find a suitable place to attach a grounding screw
Find a wire that's hot when the gear selector is in reverse, i caught the BK/PK wire behind the drivers side kickpanel at C211. (For safety reasons, the autodimming feature of the rearview mirror is disabled when backing up).
Fish two wires for the temperature probe through the firewall and mount the temp probe on the underside of the front bumper
Run the wires from below the dashboard to up above the headliner where the mirror will mount
There are seven pins on the back of the mirror, the mitocorp universal harness uses only five, the two unused output pins are for connecting the rearview mirror to the outside EC mirrors.
Below is the mirror connector from a 1998 crown victoria with compass.
If the mirror had the outside temperature display feature enabled in
it's firmware, pins 1 and 2 would connect to the outside temperature
sensor. If one had retrofitted electrochromic exterior side mirrors
from another ford vehicle such as the lincoln continental or lincoln
towncar, pins 3 and 4 would connect to the outside electrochromic mirrors.
The rearview mirror mounted on the windshield acts as a master control
for the exterior electrochromic mirrors and tells them when to dim and
to what degree to dim.
If you do not have wiring diagrams for your vehicle, you can usually find
switched +12V and ground wires at the back of the radio that you could
tap into. And the reverse light wire is usually located in with the bundle
of wires for the rear taillights and fuel pump.
There are only a limited number of places to run wires from front of car to back, underside of car is not a good location for obvious reasons, nor do passenger cars usually have the wires located between the roof and headliner. That leaves under the interior floormat, manufacturers tend to favor the edge of drivers side floor above the rocker panel since the fusebox and other required signals are located in that area. But it is possible for manufacturer to run reverse light wire above passengers side rocker panel or on top of center transmission tunnel. If you gain access to the backup light bulb sockets, there will be two wires, one is ground the other has +12volts when gear selector is in reverse. The wires are usually color coded the same at the rear of the car on the reverse light bulb sockets as they are at the dashboard which makes tracing the wire in question relatively easy.
From your local Ford Dealership as a Dealer Installed Option (DIO)
||Electrochromic Mirror Kit with Electrical
With Temperature Display
Electrochromic Mirror Kit with Electrical Harness
Salvage yard mirrors. EC mirrors first started to appear in vehicles in the early 1990s, ones with compass and thermometer appeared in the late 1990s. Insurance companies are not happy to declare high value late model vehicles a total loss unless substansial damage has been done to the vehicle. In serious collisions, the windsheild often shatters and the rearview mirror is damaged when it becomes airborn from the impact. To further complicate matters, many of the salvage yards that specialize in late model vehicles are not self service. Maybe you'll get lucky at the salvage yards, maybe not.
Online auction sites like www.ebay.com. Many electrochromatic mirrors appear in online auctions, the going rate for a used "pre-owned" basic automatic dimming mirror is usually around $25, autodimming with compass $50-$75 and auto-dimming with compass and thermometer $100-$150.
There are a few different mounting systems used by OEM manufacturers. Make sure to stay away from the cam-lock style mirror mounting system used on imports, it will not work with your crownvic without modification.
If you acquire a donnelley mirror, be warned that although the connector
is the same as the gentex mirror, the function of each wire is different.
The example connector shown below is from a 97' continental. If adding
such a mirror to a pre-1995 vic that does not have a lighting control
module, connect pin 7 "demand lighting input" to a switched +12V source
that is live whenever the ignition key is turned to "run".