clk 2006 seat belt presenter

[saundersclk]

had SRS light and safety restraint service message pop up after getting in car the other day, seat belt presenter did not hand my my belt. Had the fault code read by an independant and the fault says seat belt presenter drivers side open or short circuit. I have disconnected the plug from the motor and wish to test the motor in situ. Could somebody please tell me what wires are what so i can see if the motor has shorted out. Its been a few years since i played with any electronics on cars and the wire colours may of changed. My understanding is that there is a live, neutral and then 2/3 feedpack wires for positioning.
i'm getting a dead short between two pairs of wires and 1.5 ohms across two other pairs, which seems about right for the windings on a tiny motor?

 

[Alex Crow]

The motor is on blue and white wires going to the connector block, then brown and blue into the main loom.

 

[saundersclk]

thanks very much

 

[saundersclk]

theres no open circuit here, 1.5ohms from live to neutral. any other tests that anyone can recommend? If the motor had shorted i'd expect a dead short from live to neutral.As far as i'm aware the motors share a fuse with the rear electric windows and these are working fine. Could well be a wiring issue somewhere else.

 

[Alex Crow]

The fault code you have will not necessarily mean open or short to the motor, just as likely to mean the position sensing aspect of the unit...you did mention a dead short...

 

[saundersclk]

yes there was a dead short between a pair of the non powering wires, i couldnt move the arm in and out whilst testing as had to remove the arm to access the cable block. Would you expect a dead short from one of the other pairs when they are active? By that i mean when the motor is sensing that it is in the apropriate position. So the fault code could indicate a short/open circuit on any of the conductors ascociated with the mechanism?

 

[Alex Crow]

..........Would you expect a dead short from one of the other pairs when they are active? By that i mean when the motor is sensing that it is in the apropriate position.......

Hard to know, all I can tell you is that the sensing is electronic, not simply micro-switches.
If you really want to know, strip out the other side and test there, or Google it - lots of good info on eg Benzworld.

I have assumed you have checked for pinched wires etc etc?

If you want more help, get the specific fault code and definition, I will se what I can find out for you.

 

[saundersclk]

Have checked wires as far as I can for pinching etc and everything looks fine but i've not followed it through the full length.
Beins its not microswitches its hard to diagnose then. not had a chance to pull the other side apart yet but when i tried turning the motor the signal didn't change which is slightly worrying.
Anyone know of a good place to buy the motor from if i need a new one? Merc want about £300 for one which i find astronomical!

 

[saundersclk]

have also noticed today that the alarm does not sound when my seat belt is not plugged in whilst driving, does that alarm normally disable when the srs fault is active? i'm getting the electrics checked on friday anyway now but would love to save some money and get it sorted before hand.

 

[tinker]

Sounds like its the sensor under the seat...or where ever it is located, that would explain the seat belt presenter and the no alarm on no belt plugged in.

The car doesnt think anyones sitting in the drivers seat.....thats my guess.

 

[saundersclk]

ive checked the connections and all seems ok apart from one of the blocks is slightly loose when wiggled although the block is fully inserted.
Does anyone know what the connections are on the black box of thricks under the seat?

 

[tinker]

Im not sure where any schematic drawings could be sourced, that would be the ideal way to test this switch.

If the passenger seat works ok then disconnect the connectors one at a time until you find the one that affects the seat presenter on that seat. This should mirror onto the drivers seat, once you have located which plug then just hope it only has two connectors and its a simple normally open/ closed switch.

 

[saundersclk]

had the car checked out on fri and have been told the problem lies in the seat belt buckle, apparantly it thinks the seat belt is plugged in all the time or something which makes sense. Have tried a shot of WD40 and plenty of tapping, and fiddling but still nothing. If i need to buy a new seat belt buckle does the assembly come with the pre tensioner and everything or just the buckle?