Photo DIY - SRS Seat Sensor replacement
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Current, 90 300CE, 92 400E (Sold 95 E320,70 250C, 91 190 2.6, 91 420 SEL, 95 300D, 87 TD)
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1,767 Posts
Can someone please fill me in about the type and quality of wire used to replace if that turns out to be the problem. I have no problem with doing the repair myself, as i have completely rewired classic cars in the past and consider myself fairly handy. However I would like to take the proper safety precautions with the wire that I use to replace this. Any advice will be appreciated.
Thanks
Thanks
I used 18 gauge wiring and that seemed fine - I would not be too concerned about it because it is not taking any load and considering as it started to break the wire it was getting thinner and thinner until it broke on the last strand.
Most Any High Quality Wire..
will do the job.
To date, I have been unable to find a strap wire that is an exact replacement.
I do repair these now, and that is working well.
do solder the connections and carefully insulate ( shrink ) them.
So happy we could help.
B
will do the job.
To date, I have been unable to find a strap wire that is an exact replacement.
I do repair these now, and that is working well.
do solder the connections and carefully insulate ( shrink ) them.
So happy we could help.
B
Guys, I had to remove the side airbag from the door and I disconnected the yellow cable in the back. I plugged everything back on as it was but now I have the SRS light ON. I previously posted that I replaced the seat sensor 7months ago and before this side airbag removal the light was off. How can I fix this?
Thanks.
Thanks.
This is my understanding I have gained from tons of online research and dealing with SRS issues for the past year on my C320. Anyone feel free to correct me if im wrong:
Unlike seat sensor issues, the SRS light will not turn off on its own if there is a connection problem with the airbag. It sounds like may have tripped the code by unplugging the airbag either when the key was in the car, or battery was plugged in(I have yet to conclude which is standard procedure for dealing with SRS, some say just take the key out, some say unplug battery). In this case You just need to take the car to an Indy or the dealer, someone with the MB diagnostic system to turn the light off for you. In the case that you created an issue doing whatever it was you were doming in the door(loosened wiring, soldered joint, or connect)which it is quite possible that you did, You need to get that fixed. Once again someone with a diagnostic system can plug it into your car and both tell you what the issue is if there is one, or simply turn off the light for you. In my most recent case, the code was reading that the connection to the passenger side door airbag had a reisistance that was too hig(they called it "pass. side door airbag ignition squib" or something, ignition squib simply referring to the airbag device that explodes and make the airbag deploy) My fix was a bad connector in the wiring for the airbag in the step/sill of that side of the car, very close to where the door attaches and the wires go from the frame to the door. Its 2 wires, and the fix to just cut out the connector(used to detach wiring if the door ever needs to be removed, called "wiring disconnect") solder and seal the wires together. Then I went to an indy who has diagnostic system and they were able to turn it off. It was the third attempt at trying to turn it off after i was advised to fix three separate things, this one worked. Trial and error. Hope it helps
Yet another happy customer
May the Gods of Shade Tree Mechanics bless and keep you.:wink
It has been over 50 years since I had a seat out, and there was no electronics then. I was apprehensive, but I am retired and just cannot afford MB's labor rates. The detailed instructions and pictures made this doable.
I was having an intermittent problem with the SRS lamp so I was sure there was a broken wire - someplace.
It took a while to get the seat out and exposed on a bench but it went well from there. I stripped the insulation of the 3 wire connector close to the end back at the seat. I then used a multimeter with a sewing common pin as a probe to poke through each wire's insulation doing a continuity test from there to the plug. All was OK until I pulled on each wire. The brown lead came out. Fortunately, the break was far enough out from the seat that I could splice it. A bit of Bench Tech work - stripping, soldering, shrink tube and it was done. SRS lamp now functions properly.
The break was right where the cable was tightly tie-wrapped to a passthrough on the seat steelworks. Definitely poor Manufacturing Engineering, the cable should have been able to flex freely. Note, this was a 2001 and the wires were stranded, not solid core.
Once again, Benzworld forum has saved me money.
Thanks,
Dave
May the Gods of Shade Tree Mechanics bless and keep you.:wink
It has been over 50 years since I had a seat out, and there was no electronics then. I was apprehensive, but I am retired and just cannot afford MB's labor rates. The detailed instructions and pictures made this doable.
I was having an intermittent problem with the SRS lamp so I was sure there was a broken wire - someplace.
It took a while to get the seat out and exposed on a bench but it went well from there. I stripped the insulation of the 3 wire connector close to the end back at the seat. I then used a multimeter with a sewing common pin as a probe to poke through each wire's insulation doing a continuity test from there to the plug. All was OK until I pulled on each wire. The brown lead came out. Fortunately, the break was far enough out from the seat that I could splice it. A bit of Bench Tech work - stripping, soldering, shrink tube and it was done. SRS lamp now functions properly.
The break was right where the cable was tightly tie-wrapped to a passthrough on the seat steelworks. Definitely poor Manufacturing Engineering, the cable should have been able to flex freely. Note, this was a 2001 and the wires were stranded, not solid core.
Once again, Benzworld forum has saved me money.
Thanks,
Dave
Just want to confirm that the cheap (< US$10) seat sensor on ebay such as this one works just fine:
Seat Occupancy Sensor Emulator Suitable for MB TYPE6 W220 W210 W203 W168 W163 OG | eBay
I just cut the wire from the original seat sensor and soldered the replacement sensor box to the yellow connector and zip tied the box the the seat frame, no more SRS light.
The emulator did ship from China and takes 1~2 weeks to get here, but for the price I'm ok with that.
Thanks for all the useful information in this thread.
Seat Occupancy Sensor Emulator Suitable for MB TYPE6 W220 W210 W203 W168 W163 OG | eBay
I just cut the wire from the original seat sensor and soldered the replacement sensor box to the yellow connector and zip tied the box the the seat frame, no more SRS light.
The emulator did ship from China and takes 1~2 weeks to get here, but for the price I'm ok with that.
Thanks for all the useful information in this thread.
1959 220S cabriolet, 1983 240D original owner, 1999 E300 turbo diesel, 1988 560SL, 2003 SLK320
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3,533 Posts
GREAT THREAD!!! Thanks. Used it a lot this week when I replaced the seat bottom cover of my drivers side. Couple of things I want to mention while they are fresh in my mind. Take some photos or take some notes while you are taking things apart. I eventually got it all figured out I think, but it would have helped to have documented some things like the exact wire routing, how the seat back attaches to the seat bottom, etc. Most of it seems and looks obvious, but it all wasn't. I also had to borrow a T8 Torx for one tiny screw holding a cover on an electrical box. Never knew they came that small. My smallest one was a T10.
I took my time over a three day period, couple of hours a a day. Toughest part as others have mentioned was getting those little white clips to snap onto the wire. The new seat cover did not come with the wire BTW, so you have to reuse the old one.
All in all a very satisfying job and I'd rate it as a 7 out of 10 in difficulty. I'd much rather remove the intake manifold and change my glow plugs, but I'd rather do the seat rather than having to drill out a glow plug again.
I took my time over a three day period, couple of hours a a day. Toughest part as others have mentioned was getting those little white clips to snap onto the wire. The new seat cover did not come with the wire BTW, so you have to reuse the old one.
All in all a very satisfying job and I'd rate it as a 7 out of 10 in difficulty. I'd much rather remove the intake manifold and change my glow plugs, but I'd rather do the seat rather than having to drill out a glow plug again.
Attachments
I like this thread. My airbag light stays on (with passenger), but do not have the SRS light on (will have to check that SRS light works on key setting #2 ). My initial problem (just purchased my 99 E300D with 187k miles) was head rest does not work. I can solder and have multimeter, so good to go. Thanks.
P.S. SRS light works, but is not on after starting. Just no airbag light (by shifter) stays on (passenger or not).
P.S. SRS light works, but is not on after starting. Just no airbag light (by shifter) stays on (passenger or not).
2nd time in is a winner!!
I went into my seat again after the last failed attempt at fixing. I tried before stripping the wire cover at the bend under the seat, but my needle probe showed OK.
This time I took the seat cover off. Lot of work and probing to understand how the plastic wire grabbers/keepers come off the bottom of the seat cover. Little work getting them back on also.
After removal of seat sensor, I found an OPEN on the white wire at the module. Stripped the cover off farther along at the bend where I had stopped before and bingo, the wire was creased by the ziptie at the bend. Stripped and soldered wire together and put shrinkwrap on the wire before soldering. Taped up, checked continuity, all OK.
Thanks for this thread, really fixed a safety item.
I went into my seat again after the last failed attempt at fixing. I tried before stripping the wire cover at the bend under the seat, but my needle probe showed OK.
This time I took the seat cover off. Lot of work and probing to understand how the plastic wire grabbers/keepers come off the bottom of the seat cover. Little work getting them back on also.
After removal of seat sensor, I found an OPEN on the white wire at the module. Stripped the cover off farther along at the bend where I had stopped before and bingo, the wire was creased by the ziptie at the bend. Stripped and soldered wire together and put shrinkwrap on the wire before soldering. Taped up, checked continuity, all OK.
Thanks for this thread, really fixed a safety item.
1990 300E, 1997 E320, 1998 Jag XJ8, 1983 BMW 320i, 2002 Audi A6 Quattro
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12 Posts
I just finished replacing the seat sensor in my 97 E320 per the excellent information posted. I first checked continuity in the wires and was disappointed to find that they were intact...no breaks in the wires. I removed the sensor from the seat with no issues thanks to the play by play pictorial. I did a resistance check on the removed sensor and voila, there were two "dots" that were out of commission. An on-line dealer parts source sent me a replacement sensor mat for $133 including shipping. I replaced the mat, put everything back together and voila, the SRS light is still on. I live in rural PA where most people other than those who own a recently drilled gas well commonly avoid Mercedes Benz since the dealers are only located in the larger metro areas. Anyway, I guess I am going to have to get it scanned to figure it out from here. Thanks for the great info on this site.
Can someone come up with a test procedure for wires?
Opening Seat Sensor Box
Great thread. I got my seat out of the car today. Made the mistake of using the MB workshop instructions, which were clear as mud. Wish I checked the forum first.
Anyway, I figure I'll replace all three wires because if one wire broke, the others probably aren't far behind. Therefore, I'm going to eliminate all traces of the original solid wire completely, from the connector to the black box on the sensor. So I'm trying very carefully to open up that box, but it doesn't want to cooperate.
Does anyone have a technique, short of breaking the plastic clips?
BTW, it's starting to look to me that broken wires may be common in other systems as well. My climate control wasn't working (blew hot except when on LO). Another thread directed me to the thermistor in the overhead console. Sure enough, one of the leads was broken. In fact, the leads were so brittle and fragile, they kept breaking with even the slightest touch. MB must have gone out of its way to find the one 10k thermistor with the thinnest, most fragile, bare copper leads. Tinned or covered leads would have made all the difference without affecting the unit's accuracy one iota.
Thanks in advance.
Great thread. I got my seat out of the car today. Made the mistake of using the MB workshop instructions, which were clear as mud. Wish I checked the forum first.
Anyway, I figure I'll replace all three wires because if one wire broke, the others probably aren't far behind. Therefore, I'm going to eliminate all traces of the original solid wire completely, from the connector to the black box on the sensor. So I'm trying very carefully to open up that box, but it doesn't want to cooperate.
Does anyone have a technique, short of breaking the plastic clips?
BTW, it's starting to look to me that broken wires may be common in other systems as well. My climate control wasn't working (blew hot except when on LO). Another thread directed me to the thermistor in the overhead console. Sure enough, one of the leads was broken. In fact, the leads were so brittle and fragile, they kept breaking with even the slightest touch. MB must have gone out of its way to find the one 10k thermistor with the thinnest, most fragile, bare copper leads. Tinned or covered leads would have made all the difference without affecting the unit's accuracy one iota.
Thanks in advance.
2015 S550, 2010 E350 P1/P2, 2002 ML320
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2,670 Posts
Add me to the list of 'broken wire, but fixed' folks. The ground (brown) wire was broken on my seat sensor. I used this DIY and the WIS (for torques, 35Nm seatbelt bolt, 50Nm for the seat bolts).
One thing to note, my sensor is original with 174k miles on it. It just gave up the ghost one day. I managed to acquire a used sensor for a few bucks and found it was broken in the exact same place. The ground (brown) wire was shorted about 5 inches from the sensor control box.
Makes me wonder how many seat sensors have been thrown away due to a piece of wire...
One thing to note, my sensor is original with 174k miles on it. It just gave up the ghost one day. I managed to acquire a used sensor for a few bucks and found it was broken in the exact same place. The ground (brown) wire was shorted about 5 inches from the sensor control box.
Makes me wonder how many seat sensors have been thrown away due to a piece of wire...
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