The seat itself basically bolts onto the mechanism, so you can replace the base, but there are wires run up to the switch panel, as well as the recliner motor, that's built ino the backrest, however you can unplug these.

What has actually stopped working? Is it just the base, or has the recliner stopped too? If it's all stopped, I'd be checking fuses/breakers, and plugs. Also make sure the plugs are firmly seated into the memory module (under the seat). It could be that the module has failed, so you can try one of those first, before changing the whole base.

You can source the base, module & harness from any VT-VZ Calais with memory, or WK-WL with memory, as the motors/modules etc stayed the same. Ironically, even the Ford module from the era is the same, as they used the same supplier. There's no need to have it coded to the car, as they operate on an open can-bus signal for the priority key arrangement (where it remembers the settings for each key, and moves to them).

Sounds more like a failed memory module rather than "seat" failure - which would be 1 motor failing, and een then, failures are very rare.
I would hunt for a new module & swap it first. You can access it under the front of the seat - it's screwed to the plastic frame that holds the loom. That plastic frame is clipped into the rails under the seat.

The BA-BF Fairmont Ghia & Fairlane, as well as the FG G6E also run the same plastic loom holder, and same physical module (possible differences in pinout that I haven't confirmed).

There's a few potentials on eBay at present, but to be 100% sure I'd aim to pick up a VT/VX/WH one, as the CAN signal may be different in the later WK/WL/VY/VZ.
Also, there's a few LH ones on eBay - these are no good on the driver's side, as the switch for the LH side is flipped over, and the pin-outs are different.

Here's what the module looks like: http://www.ebay.com.au/itm/252592466332

And here's the frame it fits to: https://www.ebay.com.au/itm/253285807747

Is it a memory seat with the 3 preset buttons? If so, it needs that module to work, as all the switching is done by onboard relays inside that module. The master switch on the side of the seat connects into it, and either the switch (from user input) or the memory settings within the module (when triggered by the key, via the CAN signal from the BCM) will then operate those relays. If you don't have that module, and you do have memory buttons, then it won't work at all.

Non-memory seats have the switch connected directly to the motors. It's a single bar for up/down/tilt and forward back (6-way). When you add electric recline (8-way) it becomes a 2-bar switch, with the additional part controlling recline. Both systems can be run with or without memory, but you need the correct harness.

Memory seats also have 4 pin plugs on each motor (and therefore 4 wires to each) whilst non-memory seats only have 2 to each. The additional pair are for the encoder so the memory module can keep track of the motor/seat position, to enable it to return to the preset spot.


So getting back to what you're saying, if you have the M-1-2-3 buttons, you need to have that box, and failure (or removal) of this box will stop the seat from operating completely. Sometimes it's only a matter of unplugging the connectors & re-seating them firmly in their sockets, and it comes good.

If you don't have those M-1-2-3 buttons, then the switch is wired directly to the motors, and it's likely the switch itself has failed, or the power or earth feed to the 10-pin plug on the switch has failed. Unplug it and check for 12V+ as well as earth - when unplugged from the switch, only 1 pin will be 12V+, and only 1 will be grounded. The other 6 (or 8) will be floating.