' 90 300ce seat belt extender

[Markus]

Calling all seat belt extender experts!!!! Yes I too have disconnected the control box on the passenger side, and reach the belt at the door threshold to buckle in, but gosh darn it things should work as they are designed plus they're cool!!!

1) Passenger control box swapped into driver side, works just fine.

2) Gears are perfect.

3) Applying power directly to the extender motor, extends and retracts the arm exactly as advertised.

4) With control box installed, manually extending and retracting the arm requires considerable force. Disconnect the control box and the arm can be extended or retracted with much less force.

5) Door courtesy light switch works just fine.

6) My schematic shows a "front passenger seat contact switch, seat belt extender" I have the seat on the work bench and cannot find it. Any one know the physical location?

7) The seat belt receiver buckle appears to house a switch? How to access.

Anything I am missing here?

[glenmore]

Originally Posted by Markus

plus they're cool!!!

When I had a 91 300CE, everyone who sat in the front seat was impressed with the seat belt extender!

[Markus]

This site has helped me so much over the years I wanted to pitch in on the recent successful outcome on a project. Repairing the inoperative passenger side seatbelt presenter, and what I learned. Original post and updated responses.

Obtaining the seat belt extenders schematic for both sides is invaluable.

Reading about seat belt extenders on W124zone M104 FSM under 91- Seats and Restraints, scroll to bottom of page, Programmed repairs, sub menu 91-88042 Belt Positioner fails to extend or return. This info will cover the logic of when, where and how this system functions.......somewhat, with caveats.



Calling all seat belt extender experts!!!! Yes I too have disconnected the control box on the passenger side, and reach the belt at the door threshold to buckle in, but gosh darn it things should work as they are designed, plus they're cool!!!

1) Passenger control box swapped into driver side, works just fine.

1a) Both the control modules (boxes mounted on the extender frame) and the extenders (motor frame ass'y) are interchangeable for testing. If you are fortunate enough that one side is working as advertised, you can simply plug and play the suspected non functioning module or extender on the functional side and test. The extenders are proprietary for mounting but not for testing, and the control modules are the same p/n.
That rules out many problems (microswitches, relays, electronics in the modules, motor function etc very quickly.)


2) Gears are perfect.

3) Applying power directly to the extender motor, (black and green leads) extends and retracts the arm exactly as advertised when polarity is reversed.

3a) This bypasses the limit micro switches, so test the micro switches with a multi meter individually. Even the pushrod jammed input can be tested (and adjusted) by applying pressure against the extender arm which compresses the spring and flexes plate on which the switch is mounted activating the switch to retract the belt if jammed.

4) With control module installed, manually extending and retracting the arm requires considerable force. Disconnect the control box and the arm can be extended or retracted with much less force.

4a) That's a clue. Some current is evident, since you are pushing or pulling against partial power to the motor. This is good.

5) Door courtesy light switch works just fine.

5a) Lower switch on door jamb is an input to the system, if threshold entry illumination (light in door) is functional its probably good, as this is also an input to either retract presenter (door open) or extend presenter (door closed)

6) My schematic shows a "front passenger seat contact switch, seat belt extender" I have the seat on the work bench and cannot find it. Any one know the physical location?

6a) I believe this is incorrect on the schematic. My vehicle manufactured 9/89 does not have a seat pressure sensor. That may have been the intention for (airbag deactivation in later models who knows, but it is absolutely NOT an input on this year and model 124.051)
In fact under the seat (where the wire harness connects to all the power seat functions is one empty harness connector, that has a plastic factory U-shaped lead which connects two ends of the same wire black/red with black/pink, corresponding to seat pressure sensor, permanently replacing a closed switch, {bum in seat I suspect}


7) The seat belt receiver buckle appears to house a switch? How to access.

7a) As described in 6a, access is under the seat, move seat full back, remove black cover.
All the bulky harness wires and connectors are power seat functions, RED CONNECTORS and WIRES are SRS DO NOT TOUCH with the BATTERY CONNECTED!!
However the small black connectors are related to the seat belt buckle, and provide input to the system. On the harness side (brown yellow) you should measure 12v when appropriate (Ignition ON etc) The buckle lead is tested for functionality of the switch in the buckle.
Using multi meter to check. Open when buckled (retracts presenter), closed when unbuckled (presenter extends, provided door is cycled open and closed otherwise module retains a memory that the door has not been cycled and will not present seat belt. Makes sense as you don't want the presenter to extend every time the IGN is turned ON if the passenger door has not been cycled.)

The main inputs here (among others) are:

1) Ignition ON-OFF
2) Lower door jamb switch
3)30 second timer in the control module (retract signal if not buckled in 30 secs.)
4) Seat belt buckle

Following the schematic and testing for power at the control module input connector I discovered no current at pin 7 red/yellow, ever! This according to the schematic is supposed to be "HOT AT ALL TIMES" Bingo!!! But where does red/yellow go? On the schematic it is shown as "solder joint in harness" ????
Tracing the wire backwards it appears to run past the vacuum pump into the wire harness under the carpet in the rear passenger foot area and under the passenger seat. Bummer, not going to take out the passenger seat again, and start ripping up carpet to trace wires.
That got me thinking. The vacuum pump is also on the hot battery bus for locking and unlocking. Sure enough it also has red /yellow wire lead. Ran a test wire from the vacuum pump red/yellow to the extender control module red/yellow pin 7.
Seat belt extender worked perfectly!! Problem solved, the test wire has since become a permanent solution, and was soldered into the vacuum pump connector. It is circuit protected by a 16 amp fuse, and is never used simultaneously when the vacuum/pressure pump operates.
Now I'm not a fan of "rewiring" but the thought of removing the seats again, carpet, and splitting a wire loom to trace the break is unfathomable. But my presenters are working as advertised

[Markus]

The problem was the X48/F connectors in the right passenger footwell, underneath the carpet housed in a black plastic cover, (10 inches forward of the right rear seat cushion red release button) particularly the red/red yellow positive power supply wires. Although the connector initially appears fine, once all the old hot glue shielding is removed, reveals totally corroded through, green separated wires! Since I was in there already, there are a total of 4 connectors on this 300ce, in the same area, so I just repaired all of them. All the connectors showed some deterioration with green corrosion but not like red wires.


There are several items including the passenger seat belt extender that splice into this portion of the wire harness for power, so if you experience start experiencing intermittent operation of certain items check/clean grounds and wire harness connector splices.