721955 Replacing backrest frame
WM 721955 Replacing backrest frame
Technical values
Information
Installation position of front backrest frame
Installation position of front backrest frame
Preliminary work
1. Remove lumbar support.
-> 723419 Removing and installing lumbar support 723419 Removing and installing lumbar support
Only for seats with lumbar support.
2. Remove air cushion for backrest.
-> 721719 Removing and installing air cushion for backrest 721719 Removing and installing air cushion for backrest
Only for adaptive sports seats with air cushion in the side bolsters:
3. Remove motor for air cushion.
-> 723919 Removing and installing motor for air cushion 723919 Removing and installing air cushion motor
Only for seats with lumbar support and/or adaptive sports seats with air cushion in the side bolsters.
4. Remove motor for backrest adjustment.
-> 728919 Removing and installing motor for backrest adjustment 728919 Removing and installing motor for backrest adjustment
5. Disconnect electric plug connections at the control valves.
-> 723819 Removing and installing control valve for air cushion 723819 Removing and installing air cushion control valve
Only for seats with lumbar support and/or adaptive sports seats with air cushion in the side bolsters.
Removing backrest frame
Information
- The number of connectors and tie-wraps can vary, depending on seat equipment.
- Plug in or out all connectors going to the backrest.
- Cut and replace all tie-wraps used to secure the wire harness to the backrest.
1. Only for seats without lumbar support and/or adaptive sports seats with air cushion in the side bolsters:
Unscrew fastening screws -1- and remove the left backrest side-bolster support -2-.
Removing left backrest side-bolster support
2. Remove inner spring on backrest frame.
Removing inner spring
2.1. Disengage tension springs -1- at the left and right from the inner spring -2- ( -A- ).
2.2. Unclip inner spring -2- on the backrest frame at the drive shaft -B- and remove inner spring.
2.3. Disengage tension springs -1- from the backrest frame.
3. Cut the tie-wraps -1- at the lower part of the backrest frame using side cutters.
Cutting tie-wraps
4. Remove fastening nuts -1- from the backrest frame -2- , check them and replace if necessary.
Removing fastening nuts
5. Remove wire harness for rear backrest.
Removing wire harness for rear backrest
5.1. Pull the retaining clips -1- for the rear wire harness -2- and lines off the backrest frame.
Only for seats with lumbar support and/or adaptive sports seats with air cushion in the side bolsters.
5.2. Remove the holder -3- for the side airbag wire harness -4- and lines from the backrest frame.
5.3. Guide the rear wire harness -1- down between the backrest and seat surface -arrows-.
Guiding wire harness
Information
- Two persons are needed to remove and install the backrest frame.
6. Unscrew fastening screws -1- and remove the backrest frame -2- ( -2- ).
Removing fastening screws
Installing backrest frame
Information
- The number of connectors and tie-wraps can vary, depending on seat equipment.
- Plug in or out all connectors going to the backrest.
- Cut and replace all tie-wraps used to secure the wire harness to the backrest.
WARNING
Incorrect handling of safety bolts
- Danger of injury
- Loss of torque
-> Always use new fastening screws and nuts following removal.
-> Observe specified tightening torques.
-> Carry out a visual inspection of all re-used parts.
Information
- Two persons are needed to remove and install the backrest frame.
1. Guide the backrest -2- into the seat frame, position it and secure with the fastening screws -1-. Tightening torque => Tightening torque: 35 Nm (26 ftlb.)+/-4 Nm (+/-3 ftlb.)
Fitting fastening screws
2. Fit wire harness for rear backrest.
2.1. Guide the rear wire harness -1- up between the backrest and seat surface -arrows-.
Guiding wire harness into position
2.2. Fit the holder -3- for the side airbag wire harness -4- and lines on the backrest frame.
Fitting wire harness for rear backrest
2.3. Fit the retaining clips -1- for the rear wire harness -2- and lines on the backrest frame.
Only for seats with lumbar support and/or adaptive sports seats with air cushion in the side bolsters.
3. Fit fastening nuts -1- on the backrest frame -2-.
Fitting fastening nuts
4. Secure the pressure hose -2- and lines -3- on the lower part of the backrest frame with tie-wraps -1-.
Fitting tie-wraps
5. Install inner spring on backrest frame.
Installing inner spring
5.1. Engage tension springs -1- in the backrest frame.
5.2. Clip in inner spring -2- for bottom of backrest frame at the drive shaft -A-.
5.3. Engage tension springs -1- in the inner spring -2- on the backrest frame -B-.
6. Fit left backrest side-bolster support -2- , screw in fastening screws -1- and tighten to the specified tightening torque.=> Tightening torque: 7.5 Nm (5.5 ftlb.)+/-1 Nm (+/-0.5 ftlb.)
Only for seats without lumbar support and/or adaptive sports seats with air cushion in the side bolsters.
Fitting left backrest side-bolster support
Subsequent work
1. Install motor for backrest adjustment.
-> 728919 Removing and installing motor for backrest adjustment 728919 Removing and installing motor for backrest adjustment
2. Install motor for air cushion.
-> 723919 Removing and installing motor for air cushion 723919 Removing and installing air cushion motor
Only for seats with lumbar support and/or adaptive sports seats with air cushion in the side bolsters.
3. Plug in electric plug connections at the control valves.
-> 723819 Removing and installing control valve for air cushion 723819 Removing and installing air cushion control valve
Only for seats with lumbar support and/or adaptive sports seats with air cushion in the side bolsters.
4. Install lumbar support.
-> 723419 Removing and installing lumbar support 723419 Removing and installing lumbar support
Only for seats with lumbar support.
5. Install air cushion for backrest.
-> 721719 Removing and installing air cushion for backrest 721719 Removing and installing air cushion for backrest
Only for adaptive sports seats with air cushion in the side bolsters.