S 550 (221.171) V8-5.5L (273.961) (2007)
Seat Fan: All Technical Service Bulletins
A/C - Rear Seat Fans Make Rattling/Grinding Noises
DTB
Date:
October 2, 2008
Order No.:
P-B-91.30/121a
Supersedes: P-B-91.30/121 dated Nov. 22, 2006
Group:
91
SUBJECT: Model 221.171/176/177/179/186
Equipped with Rear Seat Climate Control (Code 402)
Active Seat Cushion Ventilation Fans in Rear Seats Making Rattling / Grinding Noise
If you receive customer reports in the above model vehicles regarding the active seat cushion ventilation fans in the rear seats making a rattling or
grinding noise, this may be due to the fan impeller contacting the seat cushion base.
1. With the seat ventilation fans activated, analyze source of the noise while changing the pressure distribution or load on the individual rear seat
cushions.
2. If the fan impeller(s) contact the rear seat cushion frame, a grinding noise will be audible. Remove the rear seat cushion assembly, refer to WIS
document AR91.12-P-1020SX.
3. Remove the seat cushion leather and seat cushion foam pad from the seat cushion frame, refer to WIS document AR91.18-P-1850SX. Complete
steps 1 to 5 only, do not separate the leather from the foam pad.
4. The two cutouts in the rear seat cushion frame (Figure 1, 2) need to be modified. The original shaped cutouts (Figure 1, pos 2) must be modified
(Figure 1, Pos 3).
5. Using a file or small grinder, remove the high points of the two cutouts in the area marked in red (Figure 2). The dimensions are shown (Figure 3).