Seems like I am working on power/heated seats all the time on my kids Saab 9000's. Got 3 of them - Saab 9k's and kids - one for each.
I think the basics should apply.
Power seats:
Generally plug and play. All the electronics and motors are under the seat itself. All you would need to do is provide a 12VDC power supply and a ground connection.
You could use any of the B (battery) jacks in the fuse block for the positive. That would allow full time operation (i.e. with the key off) Useful if you have a short wife and she doesn't put the seat back when she gets out. See below.
If key off operation is not required, plug into one of the available spare A (accessory) jacks in the fuse block. Seat will only move when key is in and turn to either RUN or ACC.
Run your ground wire to the main ground bus block. It is on the LH inside wall under the dash - up over the parking brake.
Use good wire of sufficient size to provide the power and ground. Just as long as its as big as the wire on the seat side of the harness clip.
IMPORTANT: SINCE YOU WILL BE TAPPING INTO AN UNFUSED POWER SUPPLY, IT IS IMPERATIVE THAT THE POSITIVE (HOT) WIRE HAVE AN INLINE FUSE. IT IS OKAY TO USE ONE IN-LINE FUSE AND THEN SPLIT THAT SINGLE LEAD OFF TO FEED BOTH SEATS.
ANOTHER OPTION IS TO USE ONE OF THE W (POWER WINDOW) JACKS IN THE UPPER SECTION OF THE FUSE BLOCK. DOING IT THAT WAY WOULD ELIMINATE THE NEED FOR AN IN-LINE FUSE. BOTH OF THOSE SOCKETS ARE PROTECTED BY THE FUSE/CIRCUIT BREAKER LABELED "POWER WDO" IN THE MAIN SECTION OF THE BLOCK. USING ONE OF THESE "W" SLOTS WILL RESTRICT SEAT OPERATION TO WHEN THE KEY IS IN THE RUN POSITION. BUT THE JOB WILL LOOK MUCH NEATER.
Schematic for a 1996 Caprice - same as the Impala. Note that the only wiring required to the power seat control module is a hot and a ground.:
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Saab provides a feature that allows you to move the seat with the key off when the door is open so a taller driver can move the seat back before getting in. That requires an additional ground that runs through the door Jamb switch (like the dome lights).
But I doubt the seats you are looking at will have that circuit.
The heated feature will require the control switches (they contain the relays) that mount on the dash. Power goes into the control switches. Relay within the switch assembly opens and closes as heat is required and not required. Power goes out of the control switch to the seat elements. And there is a third wire that feeds back to the control switch from the seat. It connects a thermistor in the cushion to the controller. Basically tells the controller to open and close the relay to keep the seat within the selected temperature range.
We'll have to find a schematic for that. Not tonight.
