The guys who are electronics techs in this thread are sure to know more than I do, but I did read that Germany/Austria does not permit the use of lead in solder. Don't know if that is true, but whatever the composition of the solder it seems to be subject to cracking over time. If one is going to go to the trouble of re-melting all the affected solder joints, it would seem that the better way to go would be to use a wick or solder sucker and re-solder the joint with a good electronics solder containing the appropriate lead-tin composition. Is this good info, or am I off base here?

There is a move to lead-free solder. The so called "RoHS" requirements went effective last July. There are exemptions for many industries including automotive, however not all companies use all the exemptions. The European manufacturers have been early adopters of environmental practices.

You are making 2 different points here:

1) 'When resoldering you should remove all the old solder and use new solder'.
You are absolutely correct. 100%. This is exactly what should be done. I mostly use a "Soldapult" solder sucker, but wick also works fine.

2) 'Lead solder is "better" than lead free solder'. Strictly speaking this is not correct. I have seen no claims from anyone in the industry that lead free solder is inferior to lead solder. However, it needs a higher temperature and there are several different alloys being used, so from the point of view of the DIY'er (including me) I use tin/lead 63/37 solder. This is also sometimes known as Eutectic.

As I believe I previously stated, the trouble is in the single sided PCB with no plated through holes. This type of board is cheap cra* that does not belong in a Mercedes. It doesn't belong even in a Hyundai IMHO. These boards WILL fail in industrial applications or in any application with heat cycling such as in TV sets etc.

So, remove the old solder, clean the area with a clean toothbrush, use new 63/37 lead solder.

Mike

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

I just repaired the relay in my wife's 98' C280.

To be specific about the relay location;

After you remove the carpeted truck liner, there is a large black plastic cover towards the front of the car. It is about 2 feet by 3 feet, and is held in place by three large head plastic screws, which you should be able to remove with your fingers.

Lift off that cover then locate the relay toward the right, it's easy to see and is positioned horizontally. It is the only relay that I could find under this large cover (there is another relay under a small black box, that can be accessed without removing the large black plastic cover)

Once the relay is removed, I used two knifes to pry the sides away from the relay bottom to slip off the relay cover.

I only found one, possibly two locations with cracked solder, I fixed them both of course. I didn't remove the old solder however, I simply heated up the bit that was cracked until fluid, and then added a small amount of thin resin core solder to blend in.

I realize that this isn't the way explained in other post, but I'm confident it will be adequate in this situation.

I don't know the difference between an ohm and a volt, but I want to fix my seat intermittent issue on my 98 C-class.

How much is a new relay?

Will solder and a solder gun purchased from Crutchfield years back work in repairing this relay?

I will probably just resolder on top of the original solder on the relay, any tips or mistakes to avoid to prevent a disaster?

I don't know the cost of a new relay. Hopefully someone else can chime in. Maybe 20.00? As far as the finer points of soldering that was mostly covered in previous posts in this thread, take a look. I don't know what gun/iron and solder you have. It is generally better to at least add some fresh solder (flux core). Ideally you remove the old and then resolder. It is like Sears says, "good", "better", "best".

Mike

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

Just repaired my wifes 98 C230. Thanks.

__________________
John


1998 C230 for the wife
1986 Porsche 944 Turbo for me in the summer
1993 Audi 90 for me in the winter

Bingo - Solder on Pin 2 (12 volt output) was crystalized and fractured. I cleaned out the old solder using a solder sucker and built up the solder as ray95e320se suggested. When doing the repair, be sure to use enough heat to prevent creating a cold solder joint.

1999 C280K 98,000 miles

I purchased a new seat/accessory relay for my car. The relay part# is 002-542-22-19 and my dealer charged $38.50.

The plastic panel in the trunk that covers the relay is removed by 3 plastic screws, they are not a pop-off style fastener

Nice to have my drivers seat electrics working


Scott

Hello everyone! Can someone pleae help me locate exactly where to find the fuse to repair for the seats to work? I located the small, fuse box in the trunk and also took off the carpet & black cover with the 3 screws but havent found any fuse box! I'm sure its right underneath my nose....

Thanks for the help. I am selling my car & need to get it working asap.
THANKS AGAIN!

jennifer

What car are you working on?

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

If it is a W202 94-2000 C-class then what your looking at and what where talking about here is a relay: square, grey, opaque plastic, approx 1" x 1" x 1.25" and is a seven plug connector. Mine had white script on it that read - C459703.

If you by a new one at the dealer just compare it with what is under the gray plastic shield that you removed off the floor at the back of the trunk.

I have a 99 C280...

Got the relay. replaced it and the seats now work! I cant thank this site enough and all of the helpful people! I spent $35 to replace the part. God knows how much i would have been charged if I had to take it in to a repair shop. There was NO way I could afford it! Thanks again!

jen

my car had the exact same problem with both power seats....
it either works perfectly, or doesn't respond at all... but if I turn
the key, then it works(or not).... It's been driving me crazy
for the last couple of years.

Yesterday, I decided to finally do something about it...

I found this thread and followed the advice. Bought the K24 relay at my
local Mercedes stealership for $42(!)... . Another dealer 10 miles away
sells it for only $34, but I didn't feel like fighting the morning traffic, drive
the 20 miles roundtrip, just to save 8 bucks...

The strange is thing is that as soon as I showed the parts guy the original
relay that I brought, he said "power seats don't work? we sell dozens of
these relays every week..." B In fact, he immediatlely reached under
the counter and pulled out a new one from a box of perhaps 20 of these
relays... Based on his comment and all the people who posted about this
problem, it is clear that the relay had manufacturing defect or a design
flaw. Clearly, Mercedes and Siemens must also know about this. There's
no possible reason for a relay to go back after less than 10 years.
(maybe on a Jaguar, but definitely not a Mercedes)

Anyway, I just came home' and plugged the new relay in....
THE SEATS WORK PERFECTLY NOW!


THANKS!!!

I love reading posts like this, great job.