Take the seat out. The problem is either the wiring to the seat or under the carpet right under the seat. Either way, that's where the problem is.
Look for chaffed wires. The harness is tied to the seat frame and there are sharp pieces of metal that will cut through the insulation.
Carefully cut the insulation with an Exacto knife and unwrap the tape from the wires. If it's just one wire or two wires that are damaged, wrap them individually with electrical tape and then put several layers of tape around the entire harness. Then use a piece of coffee can lid, cut into a strip to make a protector. Tape this to the harness to protect it in the future.
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