Knocking sound next to third row seat. on Ford Expedition

Problem Data
Average mileage: 118,795 (22,000–223,000)
5 model years affected: 2003, 2004, 2005, 2007, more2015
32 people reported this problem
Viewing 1 - 15 of 15 comments
Knocking sound in the back of the car when the a/c or heat is on.

Replaced the rear ac blower damper motor. = $40.00
Last winter my car was cold, when I turned the rear heat on, it began thumping loudly. Has done it ever since...
Crank up and a knocking sound from passenger rear at 3rd row power controls. Knocks/clicks about 5 times then stops.
Same issue with the knocking noise and never had it fixed. It only does it when I blow warm or cool air to the middle and back rows...