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Attached is a short description with pictures on how to fix a non or partially operational power seat switch of a 1990 Mercedes Benz 300E 2.6, but it will be a very similar process for many other Models, especially that also have the W124 chasis.

I had been driving around in an awkward position for years and decided to just try if I could fix it myself. I didn’t want to spend $186 on a new switch, especially because I wasn’t sure that was the problem.

I took the switch out, took it apart and cleaned the contacts and put it back together and it was working as new. It only took me 30 minutes. The passenger side also had problems and I decided to do that one as well and took photo’s to post an online ‘manual’.

Since I am always happy to find this kind of info online I decided to return the favor.

Thanks,

WWS
 

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Discussion Starter #3
no, it won't break it. I used a screwdriver to pop them off if i remember correctly.
 

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well your tutorial was very well done and i successfully removed and cleaned the entire switch but unfortunately it still will not budge any suggestions?
 

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Thanks WWS, that was perfect: my driver side seat switch stopped working about 2 years ago and while it's perfectly adjusted for me, anyone else who drives my car has been screwed, plus I always thought it would put a crimp on trying to sell the car ("it's a great car, except you probably can't sit comfortably in it unless you're my size!").
 

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Different Seat Switches?

Hi--

I opened and repaired the switches on my 1993 300D 2.5t and my 1995 E320. The switches on mine must be different than described here. On mine, all I had to do was pop off the black covering on the switch portion that was not working. I then took emery paper and slid it between the contact points to rub away any residue. Then I took a paper towel soaked in grain alcohol and slid it between the contacts. This resolved the problems on all but one switch. I found that the contacts to which the moving portion of the switch connects and closes the circuit get flattened after years of use. To solve this, I took small needle-nosed pliers and very slightly bent the stationary contact toward the moving portion of the switch. No problems now.

I had taken apart the adjustment switch for the steering column before and I dealt with all of the ball bearings and springs and I never wanted to deal with that again. I find my method of repairing the seat switch to be much easier and much quicker (If, indeed, the switch shown in this thread is the same as mine).
 

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Attached is a short description with pictures on how to fix a non or partially operational power seat switch of a 1990 Mercedes Benz 300E 2.6, but it will be a very similar process for many other Models, especially that also have the W124 chasis.

I had been driving around in an awkward position for years and decided to just try if I could fix it myself. I didn’t want to spend $186 on a new switch, especially because I wasn’t sure that was the problem.

I took the switch out, took it apart and cleaned the contacts and put it back together and it was working as new. It only took me 30 minutes. The passenger side also had problems and I decided to do that one as well and took photo’s to post an online ‘manual’.

Since I am always happy to find this kind of info online I decided to return the favor.

Thanks,

WWS
A very dull, but strong dinner knife (with a rounded point) is ideal for taking door panels and switches apart. With a screw driver, there's always the risk of slipping and scarring, or too much force applied. There's a pattern too...I think it's right to left in taking the cover off. Somebody did a good DIY tutorial here about taking the door panels off and covers everything door panel related.

Also, nobody ever mentions this...partly because the piece goes flying into another dimension...there is a little round plastic keeper that holds the plastic switch well fast against the door. It goes back together without it, but is much more factory with it. So far, I've found ZERO sources for that thing and am thinking about a substitute...maybe a tiny E-clip....dunno.

Kevin
 

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One side of seat works

I just bought a 95 E300 and when I lower the bottom of the seat via the switch only one side goes down so I wind up sitting lopsided. Could a dirty switch cause this problem, or do I have a bigger problem?
 

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Seat Switch

If the seat moves only on one side, it's more likely a mechanical problem with the seat than an electrical or a control problem with the switch. If it only moved up, but not down or if the forward or rear tilt didn't work at all, I'd say that it's likely that the switch could be the problem.

If you can slide the seat all the way forward, get into the back seat, locate the cable that you think drives the problematic adjustment, and try to adjust the seat while simultaneously flexing the cable in all different directions.

Some people might think that the above plan sounds ridiculous, but my sister-in-law is still driving a 300SDL that had problems with the front tilt of the drivers seat...it used to grind and growl and not adjust in the up direction. However, I found that flexing and bending the cable into all different directions of the afflicted motor/adjustment drive mechanism allowed me to find a positioning of the cable that allowed the adjustment to work again. After adding a few cable ties to keep the cable in tension and in the right position beneath the seat, no one would have guessed that there had been a problem. Six years later, it still works...I urge her to use this adjustment only when absolutely necessary, though.

Seriously...getting into trying to repair cables and drive mechanisms can be a real headache. Used mechanisms are sometimes hard to swap (often because a different portion of the seat bottom adjustment mechanisms has gone bad). Buying new parts from the dealer is dodgy and trying to engineer an internal fix can be really difficult.

I wish that Mercedes-Benz had created a facility for manually cranking the seat into position in case of mechanical failure. I owned a Volvo that had a tool to which you could attach a handle or a drill and independently move each side of the seat bottom and seat back mechanisms without relying on the motors. I don't know whether or not this is still the case, tough.

If you get the seat into a position that you like, I'd disconnect the portion of the switch that controls the problematic adjustment. Good luck and please keep me informed.

I just bought a 95 E300 and when I lower the bottom of the seat via the switch only one side goes down so I wind up sitting lopsided. Could a dirty switch cause this problem, or do I have a bigger problem?
 

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Seriously...getting into trying to repair cables and drive mechanisms can be a real headache. Good luck and please keep me informed.
UPDATE: Did just like you suggested and wiggled the cable that goes to the rear motor on the side that wasn't working and...voila! Works like a charm. Thanks for the suggestion!
 

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Success!

UPDATE: Did just like you suggested and wiggled the cable that goes to the rear motor on the side that wasn't working and...voila! Works like a charm. Thanks for the suggestion!
Glad to hear that you achieved success. Sometimes the problems are in the ends of the cables, which are compressed springs and shaped into rectangles at their ends. The ends can round off or the cable can lose rigidity at an end and it will spin in the gear drive. sometimes both the cable and the gear drive are the problem and it's not easy to repair without needing to get creative. Either way, make certain that if you ever hear grinding or slipping noises as you use the adjustment, stop immediately until you can do another wiggle under the seat to see if you can get it working again. The grinding, even if it is temporary (motor grinds/seat moves a bit/motor grinds) will make the problem worse and ultimately impossible to fix again without taking the seat out and looking at the components. It takes the right combination of cable angle, cable tension, and making certain that the end of the cable is wedged into the gear drive. If it works quietly and doesn't slip out of operating normally into a mixture of grinding and operation, it's functioning in almost the same way as when it was new...it's not like new, though--it's better because you got it going again.

Since you've gotten it moving again, use as many cable ties as you need to keep the cable kinked in its present state. Make certain not to obstruct any other mechanism or to impede the seat's movements. This should take only a little creativity and maybe some bloody knuckles. Avoid moving the cable, especially when vacuuming under the seats and try to keep items from rolling underneath the seat from behind. Give it a few months and you can be a little less worried about it.
 

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I did it an easier way. The passenger side head rest and upper seat adjustment switch were problematic but not the lower switch. (93 400E)

Went down to the local wrecking yard and pulled one from a 190E (same switch panel), since Merc models are scarce in my area (maybe five in the whole yard) .

All is working now except the switches that adjust the height.

Tried to disassemble the original switch but one switch cover needed extra force to get off and a plastic piece inside was damaged. So be forewarned to be extra careful taking these things apart.



The switch panel is upside down. The top three switches, ^above^, control the lower portion of the seat. Tilt and forward/rear posistion.

I just wanted to show what the newer switch panel looks like inside
 

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I didn't have a lot of luck prying the switch contact covers off. I knew they were going to break if I kept on prying. So I dunked the whole switch in a vibrating cleaner for a half hr. Switch worked great until I decided it also needed some sort of lubricant. I sprayed DeoxIT in there, which is safe on virtually all electronics....and it quit. Frustrated at that point....found one on ebay from a junk dealer in an arid climate, with a guarantee. Installed in a few minutes and good to go. Cost about $30 with shipping....just saying.:rolleyes:

Kevin
 

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1995 e320 seat switch

Hi--

I opened and repaired the switches on my 1993 300D 2.5t and my 1995 E320. The switches on mine must be different than described here. On mine, all I had to do was pop off the black covering on the switch portion that was not working. I then took emery paper and slid it between the contact points to rub away any residue. Then I took a paper towel soaked in grain alcohol and slid it between the contacts. This resolved the problems on all but one switch. I found that the contacts to which the moving portion of the switch connects and closes the circuit get flattened after years of use. To solve this, I took small needle-nosed pliers and very slightly bent the stationary contact toward the moving portion of the switch. No problems now.

I had taken apart the adjustment switch for the steering column before and I dealt with all of the ball bearings and springs and I never wanted to deal with that again. I find my method of repairing the seat switch to be much easier and much quicker (If, indeed, the switch shown in this thread is the same as mine).
How did you actually take the black covering of the switch portion off? I am having a hard time doing that and I am afraid I am going to break something...thanks
 

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my switch got wet (left the widows opened overnight) and caught fire on the passenger side yesterday(1993 300E).
got it to stop when removing the 2 fuses for the seats.
It worked again the next day but was so melted on one side that I removed one plug .
I still can work the seat up/down forward /backward but not the backside or the headrest.
Is there a way to adjust the backside inclined manually while waiting for a replacement part ?
I also had to cut one of the 2- wire connectors from the harness.
Can I buy this connector separatly without buying the full harness?
Thanks
Francois
 

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my switch got wet (left the widows opened overnight) and caught fire on the passenger side yesterday(1993 300E).
got it to stop when removing the 2 fuses for the seats.
It worked again the next day but was so melted on one side that I removed one plug .
I still can work the seat up/down forward /backward but not the backside or the headrest.
Is there a way to adjust the backside inclined manually while waiting for a replacement part ?
I also had to cut one of the 2- wire connectors from the harness.
Can I buy this connector separatly without buying the full harness?
Thanks
Francois
To adjust manually, you have to remove the seat to get access to the cables that connect between the regulators and the seat motors. Remove the appropriate cable from the motor (leave it in the regulator), attach a drill to the end of the cable to adjust.

In one case I saw someone had left the [cordless] drill attached (where it was still accessible) and re-mounted the seat. He left it that way so he didn't have to replace the motor... until his wife complained "What the hell is that?!" So he replaced it. :D
 
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