power seat issue-intermittent operation (help)
 

i have been over and under my 99 c280 and can not figure out why the power seats work when they want to, so here's what i've done so far after using the search option........replaced the aux relay in the trunk next to the battery, checked all fuses, and examined all wiring and harnesses under the seats. here's where i am baffled because i was thinking after all the troubleshooting that i had an intermittent open somewhere (broke/bad wire), but that would only affect the seat with the problem, whereas when mine won't work it affects both seats. Now i'm thinking that there may be another relay coming from the power source, but i can't find one. Can anyone enlighten me?
:nix::confused::confused:

155 views and not a single response, is this a rare problem in w202's?

Check your pm,sent you a reply

adding one more on seats / motor ideas welcome.
 

Need your help, folks.
C280, 1996. I had a metal flashlight wedged beneath the front passenger seat (my fault), removed it and now the seat won't budge with the motors...no movement on seat/back/headrest. Fuses are good in the engine compartment, but none of them seem to be for the seats. Am I missing a fuse or relay somewhere?
HELP! my taller friends are ready to abandon me because the seat is so far forward.
all ideas welcome.
p.s. just had the car detailed for the first time. It is well worth the money to change the image in my head for this Benz.

Rear compartment(Trunk) convience relay under the plastic tray above the spare tire area. The soldering comes loose and cuses the seats to not get power all the time Take out the rug and you'll see a plastic cover held there by three plastic screw heads remove them and the relay is right there on the right side.

got a new relay on order, checked the wiring for continuity and physical appearance and all looked good. i'll know for sure when new relay comes in. Local cost 68.00 + tax, online 24 + 3 to ship.

My 1997 C200 facelifted suffers from the same problem. Would really want to know how to solve it.

:bow:

I had this problem (2000 C230 sport) so checked the fuse box in the trunk. All looked fine but the cover was cracked so would get pushed down on to the fuse box. The fuse box is a bit wiggly. I used duct tape to repair the cracked fuse box cover so now it does not allow the trunk carpet to push the cover down on the fuses. My problem now seems to have gone away, but it was sporadic before so I will report back if it ever returns.

Like I posted before check the convience relay located in the trunk area. take out the carpet and there is a plastic cover at the top near the seats. Unscrew the 3 plastic screws and the relay is on the right side. These are Bosche and are very apt to have the solder crack. Either replace the relay or if your mechanically inclined you can take it apsrt and heat the solder to make it reflow. Problem solved.

Bumping this thread - I have the same problem but...
 

...over an hour at the dealership service lane while two techs and the svc mgr looked EVERYWHERE for the white comfort/convenience relay.

Note that mine has no seat memory or seat heat. 1999 C280, US Specification. We removed all trunk trim, the back seat, both underhood electrical box covers and inspected under the seats (as best we could).

Nothing. No relay. My seats are very intermittent. Help!

In my 2000 c230k the relay is in the trunk. You need to pull the carpet that covers the spare completely out. Back behind the spare tire there is a black plastic deck that covers the trunk floor. It has with large plastic "screws" that hold it down. Remove these and pull out the plastic deck and you should see several comfort and convenience electronic components (like the Tele-Aid phone communications equipment by Motorola). The relay that needs replacing is on the passenger side.

My son took the car out. When he gets back I'll take some photos and post them for you.

Here are photos of where to get to the seat relay.
First one shows the plastic deck piece that is found once you take out the carpet. Red circles show the screw caps that you unscrew to remove deck.
http://ostrom.uthsc.edu/documents/c230trunk.jpg
Next photo shows the location of the relay. These tend to have a bad weld inside so needs to be replaced.
http://ostrom.uthsc.edu/documents/c230relayloc.jpg
Final photo is close-up of the relay (put part number into eBay to find a replacement).
http://ostrom.uthsc.edu/documents/c230relay.jpg

I hope this helps. This is a very common problem in W202's but an easy fix.

Genius
 

Thank you very much for taking the time to post those pictures of the relay that's what we need it, some pictures and you save a lot of people some time and money thanks again and god bless you and this is a good site.

I had this problem on my 99 MB C280 and i read this comments about removing the power seats Relay and many people open the relay an fix it by doing solder work come on guys the relay only cost $35 bucks at the Mercedes dealer i went and buy it and put it on and there is now power seat working back to normal.thanks for Rostrom who post the pictures about were the relay is located have a good day guys and don't be sheepoo.

Huge thanks to Rostrom for the detailed pic's! I called my local MB dealer to discuss the problem and I might as well have been talking to the wall! $35 delivered using Google shopping.

Soldering
 

For zero bucks and a small soldering iron, and about 5 minutes work, and normally it's the right fix.
$35.00 compared to zero seems a bit foolish not to fix it yourself.

Zero Bucks?
 

Well, you have a good point. However, not all of us are handy and/or own a soldering iron. So, I'd have to buy one (I'm sure they're less than $35) and then hope that I don't burn out the circuit board on my first try! I'm not sure how your reply was helpful but thanks for your input...

I agree with you comment " I'm not sure how your reply was helpful but thanks for your input..." but if you follow the general trend of questions, most people are on a shoestring budget. Possibly you and I are the odd exception, but I love to tinker, although I can afford not to, which is my choice.

So this is what you had to contribute to this community ?. Do not forget this is DIY site and people enjoy resolving problem by various method. There is nothing wrong with fixing the part if they can or learn how to.

I have the same issue, can you please post part number so I know what to buy.

My 1999 C230 power seat stopped working and after some troubleshooting found that "GREY WIRE" going into harness in shown picture from rostrom's was not touching to harness correctly. I pushed wire to harness and stick in the pin to have better connection and power seat started working. I am planning to do some soldering there so it stays there.

Thanks for picture. It helped me to identify the problem where my mechanic want to replace Comfort Control Unit from other old car and charge me $200.

Anybody know the alternate location where MB put the comfort/convenience relay? Mine is not under the plastic cover. 1999 C280, USA spec, no seat heat or memory.

Where did you solder ?. I tried to fix buy moving grey wire on harness and it worked for couple of days and now it is not working. I am not sure if changing relay will fix the issue. What could go wrong in relay ?. Before I buy relay I want to make sure it will fix the issue.

You have to take the relay out of the car, and open it up. You will find loose or cracked solder joints inside - they must be carefully resoldered, or you can always purchase a new relay for around $50.

It isn't surprising that your grey wire fix worked briefly - usually the seats become intermittent before failing entirely.

Sadly my problem is that my relay is not in the standard location - I know exactly what to do and how to do it, but I'm waiting to get more guidance on alternate locations before simply tearing the car apart. Fortunately mine still work if I turn the key slowly to on while pushing the seat control - and they will work for a few minutes.

Bought new relay for $35 ebay and solved problem. I wish I would have replace it long time ago.