[FPB111]

One other part to check is the heater control bolted to the bottom of the seat pad plastic frame. It looks like a relay. I’m not sure how to check it other then swapping it with the other one from your passenger seat.

You can get new heater grids with new cushions for ~$150 each or just the grids for ~$80. I have never purchased backs just bottoms.
They are glued to the foam. I have removed the grids and reused them on other foam. If you do remove the old grid it does pull some of the thin foam with it.
Next time I need to replace one I will buy the whole thing, heated seat bottom or back. Think about how packed your old foam is it makes sense to just replace it. It is less hassle and nice to have a comfortable new seat.

If you buy the foam pad make sure to get the correct one. Sport seat have less padding under your butt and higher side bolsters. I have a couple of comfort seats that I have been scavenging parts from. No bottom foam or heaters left but back bolsters & heaters, motors, switches etc are still around and for sale. The seats are black, comfort, full power, full leather, memory seats in very good condition. If you need any bits let me know.