Happens to any heated seat if there is piecing damage (studs on some jeans will do it) into the heated mat. Or 20-30 years worth of butts have worn the materials down until point of failure.
You can't get genuine mats anymore. Sometimes they just glue onto the foam base sometimes they are sort of built in. Best if to get the base foam from another car (see my recent thread on part numbers there are 2 or 3 different seat base foam shapes) for 850,x70 and c70
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