I am really cheap! When my daughter's 850 seatback died, I looked at Bay13 and started to investigate. Knowing that the cable had stretched, I cut off the hog clips at the bottom of the seat back. Then I reached my hand up and found the motor and cable at the driver's side door of the seat. I pushed the cable toward the motor about 1/2mm, and tried the switch. It worked. Replaced the metal hog clips with plastic zip ties, cut off the excess plastic, and everything still works months later.
The local dealer wanted to replace the cable for mega bucks.

Klaus
PS $3000 for a sunroof replacement? Not in this household, that would buy a replacement 850! If the ABS/Tracks light is on, Voc Rocha will fix it for $150.
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(V♂LV♂s 1995 854T, 1998 V70R)