this guy saved me 800 dollars that the dealer wanted. just spent 5 bucks on solder! thank you so much. I had all kinds of message lights all gone now

Maybe you forgot to mention, that this resoldering you did, solved me some scan error codes, EGR errors, Sencondary Air pump error, and downstream, the four Oxigen sensors error codes. This relay feed power to the secondary air pump (exhausting gases into manifold), and this bad relay connection is responsible for bad idling, plus poor exhaust gases processing in the catalitic converter... Took me 2 weeks to realize and solve this fault. Now my car is like a rocket again... SLK320 Great BTW... Hope this tech add on help others... Cheers

thanks from NZ, got on my car today, battery and their terminals all good, but no cranking starter, radiator fan on full spin, watched your u-tube video, fixed in under half an hour, , mine looked oxidized on the right of the 3 terminals of the top left connector ... same place as yours ... glad this happened at home ) ... kudos

Great help mate.Saved me from loads of trouble.Located in Greece, just re-soldered the contacts and problem's solved. The car is even running sharper after the fix! Could never imagine that such a small thing could affect the car so much.Thanx again

Had indicator problem.Followed the instructions on the video.Resoldered the print and cleaned all contactpoints with 1200 sandpaper. Put the unit back and it works fine. Took me less than an hour. Many thanks!

just bought 2003 slk great to see videos that I can use, Great service, Thank you

Thanks for this. I checked my K40 on R170 SLK 230 and could see the bad joints. Resoldered in minutes and saved £££.

I have just done this fix on our 2000 R170 for the third time in about 6 years, many thanks. The symptom is no supercharge and this fixes it. What I don't understand is why it fails every couple of years. The solder looks ok each time but I reflow it and bingo.

Bought a new relay from Rock Auto turned some screws under dash by steering wheel removed old relay put in new one TA-DA both power seats work, saved a bundle! Big THANKS

Thanks good instructions. I have a 1997 e320 and have had a terrible time finding any info on replacing it or even where it was. Gleaned from this.

Thanks for the information. Just to add...don't be fooled if your terminals look OK...... Very close inspection under a magnifier will probably reveal a dry joint of the pins through the the solder joint. Best to re-flow the joints.

Aaron your the man, just did this and it worked, back to full power. Thanks buddy.

i had the same thing, took out the k40 relay it looked find, had it inspected and thought hmmm, after playing with the relays, decided oh well put it back in and it started working, so worth a try.

Thank you so much, this worked! - supercharger is engaging again and not throwing codes anymore. Thanks again so much. While it was out I gave each relay about 9v to make sure they actuated, the middle two are linked together. Wasn't too much burnt area but there was tons of grit and grime on the contacts.

Thanks for the vid, checked the solder points on mine and all was good. looked about and found a loose boost pipe on the underside of the supercharger. tightened it and sorted the problem of supercharger loose half way in 3rd gear.

does this have anything to do with the supercharger? I have boost problem my supercharger not making boost I feel like I have like a 100HP less not

Holy grail repair....so much frustration and you put it on a vid. .....thank you

Can you make a video of a 2004 SLK 230 no start and no crank where the main fuse is located?

I tried it on mine but hasn't solved issue of lights all flashing and the fan coming on. May have to buy a new module. Merc want £175 just to test it so may as well buy the unit for the same which I think they cost now.

Tks for taking the time of making this video... and help the group...

Good job! Excellent video, nice and slow and clear, yet not all day. Bravo!!! Thanks for posting. I've actually already done this fix, but it was fun as a hoot to watch someone else do it :)

Thx so much, you save my Day 🙂

The board in my SLK200 2002 isn't quite the same - not sure if mine has been replaced at some stage but the part numbers are worn off for some reason and all the soldering looks pretty micky mouse TBF. All the joints are in the same place, just a slightly different pcb.

Great video, one question: Why don't you clean the damn engine bay? It's a machine, not a garden shovel, clean it.

Had the same problem several months ago. Had my mechanic friend do the solder and it was fine. Maybe 300 miles later while 60 miles from home the same problem, rough running, poor power, check engine light. Will have him check for codes (probabably the same 4 as before) and will replace the K40 with a spare I bought. A check on the SLK site indicates that there could be hairline cracks so I'm not going to screw around with this anymore. Have had this 99 less than a year. Makes me think I should of got a Miata orZ3.

Very clear vid thanks, So what does the relay do to affect other systems? What were symptoms before the repair apart from rough idle?

Hi Aaron - what problems were you seeing with this defective K40 relay? Was you car stalling when you come to a stop?

Thank you very informative 👍 I will have a look later today, problem I'm having is windscreen washer pump not work ,tested pump ok so wondering if anything in this board might affect it 🤔 kind regards mike.

When you put it back in does have the battery unconnected cause errors?

when I bought my 1996 E300 D, the speedo did not work and some dash lights (I don't remember if it was the ETS or ABS) I re-soldered and it fixed it. But, recently my ETS was being intermittent, and now it's on full time. Do you think it could be the K 40 again? Before I fixed it, it did go into no-start, and recently it has not done that (yet).

I resoldered all solder spots before to fix mine. I jabe a huge parasitic draw in my car and its coming from this relay board. Any solutions? Do I need to find another board and start over?

Hi, i have missfire at 3rd cly in my 97’slk230. I have changed plugs, coils, cables,cps and maf sensor . nothing changed. Service tried all but they say its about ecu. Do you have any suggest about it? Or did you heard about same problem before?

Great Video Aaron, very clear in what had to be done. Thanks.

I took my 2000 SLK230 with 42,000 miles for a short drive around my neighborhood this winter. After less than a mile, the car just just off. I pushed it home with a neighbor. An hour later it started. Tried it again weeks later and it was dead, although the battery had some juice. Jumping was no use. So today I removed the K40 and it looks fine. I cannot see any bad solders. Can it be tested to see if the problem really is with this module? The battery is recent and the alternator was replaced already.

Bonjour, je cherche le relais centrale clignotante. Avez-vous une idée. Merci a tous de m'aider

Thanks to you I managed to disassemble and weld my fucking K40 relay with a DTC P1236 on my 230k 2000 Aaron you roxxxxx 👍🏻

Anyone ever diagnose the small blower motor inside the ECU/Relay box? Looking for a video showing removal/replacement.

I did this and the car ran great... but then I shut it off and when I went to start it again after it cooled down she wouldn't start.. cant hear the fuel pump... act like it not getting fuel... do you know what could be wrong and how to fix it? Thank you Brenda

I'd like to know what all the k 40 relay controls? My roof will not come back up. I have had everything related to it fixed at least once. I'm not losing hydrolic fluid and I can hear the motor working. the trunk lid opens and the windows go down but the lid will not come back up. any help would be much appreciated. best, Roger

Have you ever done any work on the supercharger? Such as repair leaks and replace bad seals? Mine is leaking and fouling up my MAF sensor, causing my check engine light to stay on. I've cleaned my MAF twice, tried to reset it several times by s couple different methods and the only thing I can figure is that the supercharger is leaking oil and causing it to stay wet, thus keeping the CE light on.

Tnx for this video,i have a problem that I have identified, but the car is turned off suddenly

Great video, thanks man! I had the same problem on my slk 230. Works great!

If you are already on that clean your throttle body (which is easy) and look at your air filter if you want to replace it (super easy)

does clk 200 136 hp has this?i have rough idle cold start even in the summer

Got someone to solder mine and now fan isnt running properly and central lock

you would think merc would address this problem after all these years with these k 40 relays...but nope

On my 99 SLK 230 whenever I'm in D the vibration is really rough, the car ran fine. Could this k40 relay cause this problem.

How do you fix the connections for the electric seat relay? I need any info on how to fix my electeic seats before committing on buying a new relay box.

Well done Aaron very useful Video.

Very helpful. Thank you, kind sir!

do u get any codes after putting it back in because battery was disconnected.

My front seat wont scoot back, i hear the little motor going but it wont move back, i cant fit in my car! ,HOW do i fix it??????

hi can any body help me pleas when I start my 230 slk it sound if it only run on 3 cylinders

very nice job .... nice demo :) *****

Do you know if this will cure the indicators not working problem?

much appreciated and well done

This is very helpful. Thanks

This works great except my K40 Relay is on the right side :) Thank you

Muy buena ayuda amigo. gracias desde chile

dose this work the the sedan model too? 99 c230k

Is that your brake wear sensor light on?

Cool video dude

Hi, this is Dean from HK, i saw your video and i would like to ask, when you remove the K40 relay then you use some kind of spay to clean the relay up? then the problem will be solve? Please advice thanks

i have the same problem too . did you find out what was wrong with yours ?

Thx but nothin found on mine all solder connections were good ....process of elimination

hi buddy can i clean it with CRC 05101 QD Electronic Cleaner

Wir lieben den Mercedes SLK 💝 Wir restaurieren einen '96er und haben viele Videos mit wichtigen Tips und Anleitungen zum Selbstschrauben für Euch produziert. Ihr findet die Videos auf meinem Kanal: clubblendorange 🎬📽👨🏼‍🔧