[efair]

You can't see the imperfections visually - they're hidden. Just re-flow all solder joints (or take to someone who can solder and have them do it (or just replace the K40)).

 

[Sevecaraddict]

I have a 2003 SLK230 6spd manual w/23k that I 'parked' last Summer when the top sprung a hydraulic leak and I didn't have time to mess with it. I put it under a carport and a few months later robbed the battery out of it in October to put in a BMW X3 I was selling. Fast forward to last weekend and the weather is getting nicer and I'm ready to work on my baby Benz and I put a new battery in it and she will spin over, but won't start.

A quick Google search leads me here. I pull the K-40 relay and inspect the solders and they all look good. I can make the car run by touching 2 contact points together on one of the coils and hold them in place. She runs like a champ. Let go of those two contact points and the car dies out. If I'm certain its the K-40 relay, I don't mind to order a new one. I just hate throwing money at a problem and NOT fixing it.

 

[jbanks15]

I have a 2003 SLK230 6spd manual w/23k that I 'parked' last Summer when the top sprung a hydraulic leak and I didn't have time to mess with it. I put it under a carport and a few months later robbed the battery out of it in October to put in a BMW X3 I was selling. Fast forward to last weekend and the weather is getting nicer and I'm ready to work on my baby Benz and I put a new battery in it and she will spin over, but won't start.

A quick Google search leads me here. I pull the K-40 relay and inspect the solders and they all look good. I can make the car run by touching 2 contact points together on one of the coils and hold them in place. She runs like a champ. Let go of those two contact points and the car dies out. If I'm certain its the K-40 relay, I don't mind to order a new one. I just hate throwing money at a problem and NOT fixing it.

Welcome to SLKWorld.com: The #1 Mercedes-Benz SLK Forum from Florida!


Join the gang! Your 1st thread should be your introduction so we can welcome you properly so post an introduction in the ‘New members introduce yourself here’ section, if you haven’t already. New Members Introduce Yourself Here - Mercedes Benz SLK Forum

Some tips to make your visit here more enjoyable:
If you haven’t, please use the 'search' feature at the top right of the page for your questions as they have probably been asked before. Remember, ‘Search’ is your friend.
If you wish to become PM (Private Message) capable or to ‘edit’, you need 15 posts. To get those 15 posts quickly, just go to the ‘New members introduce yourself here’ section and welcome enough new members to obtain your needed posts to PM/edit. You can always pm a moderator.
Want to post a picture? Start a new thread or make a post, click ‘edit’, click on the ‘paper clip’ or ‘advanced’ and/or ‘manage attachments’ then ‘choose file’ then ‘upload’ and ‘submit’! If Iphone pics, you need to rename any additional pics as Iphone names its pics all the same, image.jpg.
Want to ‘like’ or thank’ someone’s comments? Use the ‘like’ button to the right or the ‘Thanks’ button, bottom right of any post you like. This saves you having to comment.
New members should be aware that the 'New Posts' link next to the 'Search' link top right of the info bar is a great way to see all of the posts you have missed since you were on the forum last. Remember to click 'mark forums read' under ‘quick links’ when you leave.
FREE!! Post your vin in the Vehicle Datacard Request section to get a free datacard (options on your car). You must update your profile with vehicle info and your location and post an introduction first.
http://www.slkworld.com/vehicle-data-card/67706-free-how-get-free-datacard.html

Thank you
Jeff
Moderator/Founding Member/Ride of the Month Coordinator

 

[Sevecaraddict]

I went ahead and spent the $180 for a new one. Fingers crossed that this fixes it. I'm selling my Lexus CT200h F-Sport and planning to make this my 'daily' for awhile.

 

[jbanks15]

Join the gang! Your 1st thread should be your introduction so we can welcome you properly so post an introduction in the ‘New members introduce yourself here’ section, if you haven’t already. New Members Introduce Yourself Here - Mercedes Benz SLK Forum

 

[muskey67]

hi you also get cold solder joints in the multi purpose module which is opposite the k40 up to 2002 which affects the roof and many other things, ive just had to resolder mine to get the roof working again this might be helpful to.

 

[Sevecaraddict]

Installed the new K40 and my car fired right up. It was well worth the money spent to make sure it doesn't give me future problems.:smile:

 

[CRUISER1]

Hi, Please could someone help me I have an SLK 230 R170 with possible symptoms of a K40 relay fault. Fast engine fan but no engine crank.
Fuse number F2 and F3 on K40 relay are getting no power but they are not blown. The other 4 fuses do have power. Please could anyone advise which connector powers the fuses F2 and F3 on the K40 relay?
I can not locate the connector to fuses F2 and F3 on the R170 K40 wiring diagram. Please could anyone advise which connector powers the F2 and F3 fuses on the K40 relay?
Any help is greatly appreciated thanks.

 

[sinbad]

No SC operation and EPS/BAP with CEL.

These are 2 of the symptoms my car has intermittently. Once it has heated to normal the BAP/EPS will go out and I get SC operation again. think this is it? I cannot check myself due to health issues but will try nit if it is familiar with my new thread on my issues. THX! Mark

Hiya
Not sure if you ever got resolution on this, but I am having similar problems on my 32.
Codes pulled were both upstream O2 sensor heating circuits not working, supercharger mechanical failure and secondary air intake switchover circuit bad.

I think it's in the relay module, and my thinking is as follows:
This module basically provides power to all the engine sensors and components. Each feed from this module runs several components (which is why when you get a certain combination of DTCs, it points to the relay module). Different set of DTCs, different feed circuit.
One pin on this module on the 32 provides power to: Supercharger clutch magnet, SAI switchover solenoid, and both O2 sensors.
Investigation of this circuit has shown me that when current is drawn by some components (eg, the O2 heaters), the voltage on the circuit drops to 10.5V - This is outside the tolerance for the ECU so it throws errors for all four circuits. (This incidentally would also explain why these cars are so sensitive to dodgy batteries - small voltage fluctuations cause the ECU to mark circuits as bad).
I've checked the individual components on this circuit, total current that should be about 6 amps based on the resistances involved (9.5 ohms x2 for the O2 sensors and about 3.5 ohms for the SC clutch). 6 amps should not be enough to pull the voltage down so far, so something upstream is choking the current. My current theory is a bad solder joint or contact on that particular pin/path on this module.
I'll be pulling it tonight and inspecting it... Will provide feedback.

And here we have it.

Fixing that has fixed the error codes I had

So for the code cluster:
P2024-002 (stored and current) - Y32 Air pump switchover valve - P0412
P20BE-002 (stored) Right O2 front sensor short to ground
P20BF-002 (stored) Left O2 front sensor short to ground
P2008-008 (stored) Heating of front O2 capacity too low
P2088-008 (stored) Heating of front O2 capacity too low
P207c (stored and current) Supercharger mechanical fault (omg)

Relay module pin A3 is most likely your culprit.
Symptoms - Severely reduced power (I had to manually change down gears to get up hills, 120km/h was out of reach). BAS/ESP light. Check engine light.

 

[El_Murcielago]

@sinbad

Great work!!!

Someone at Mercedes needs to go out and hire a guy from the Japanese car industry to fix the quality control on all those electronics. It's outrageous that there are so many solder joint failures causing expensive and tricky problems. These electronic problems seem to be the proverbial Achilles heel, and are destroying the brand's quality performance. Seems like a simple fix too. Makes one wonder why they haven't already done it.

Either that, or outsource all the electronics to Denso or some other Japanese supplier. That might get Bosch's attention.

--Kim G

 

[Wayne1965]

K40 repair

I have just repaired my k40. The car had a fuel leak but was running and power roof worked. I had the fuel leak repaired and the car mot'd. On the way back from the tesy station the car spluttered and stopped running. When i got the car home and tested for fuel at the schrader valve, there was no fuel, and also the roof no longer worked. On looking aroung on tinternet i came across several posts about the k40 and its problems. I took the k40 out of its housing, but left it electrically connected and noticed that 3 of the 5 relays on the pcb looked discoloured (windings looked yellow instead of bright copper), on further investigation it turned out that the relay for the fuel pump wasnt closing to energise thr lift pump. Manualy closing the fuel pump,relay restored fuel to rail and the engine would now start and run. Out came the k40 pcb, and i had dabbed a 12v feed to each of the relay coils to check operation and found that 2 of the 3 discoloured relays would not operate. I located a supplier on ebay (and paid too much for new relays really), but fitted new relays to all 3 discoloured ones. When the k40 went back in normal engine operation and roof operation was restored. Very happy bunny.

 

[jbanks15]

I have just repaired my k40. The car had a fuel leak but was running and power roof worked. I had the fuel leak repaired and the car mot'd. On the way back from the tesy station the car spluttered and stopped running. When i got the car home and tested for fuel at the schrader valve, there was no fuel, and also the roof no longer worked. On looking aroung on tinternet i came across several posts about the k40 and its problems. I took the k40 out of its housing, but left it electrically connected and noticed that 3 of the 5 relays on the pcb looked discoloured (windings looked yellow instead of bright copper), on further investigation it turned out that the relay for the fuel pump wasnt closing to energise thr lift pump. Manualy closing the fuel pump,relay restored fuel to rail and the engine would now start and run. Out came the k40 pcb, and i had dabbed a 12v feed to each of the relay coils to check operation and found that 2 of the 3 discoloured relays would not operate. I located a supplier on ebay (and paid too much for new relays really), but fitted new relays to all 3 discoloured ones. When the k40 went back in normal engine operation and roof operation was restored. Very happy bunny.

Welcome to SLKWorld.com: The #1 Mercedes-Benz SLK Forum from Florida!

First please update your vehicle (model?: 32, 200, 230, 320) in your profile as it helps the members answer your questions which usually are based on that information if you haven’t. This takes about 30 seconds to do.
Follow exactly to update: ‘Usercp’ at the top of page, then ‘edit your details’ on the left side, ‘additional information’ near the bottom, edit your . Info in your garage does not update your profile.

Join the gang! Your 1st thread should be your introduction so we can welcome you properly so post an introduction in the ‘New members introduce yourself here’ section, if you haven’t already. http://www.slkworld.com/new-members-introduce-yourself-here/

On a smartphone: http://www.slkworld.com/new-members...troduce-yourself-here/330737-how-update-your-profile-post-intro-smartphone.html

If you haven’t, please use the 'search' feature at the top right of the page for your questions as they have probably been asked before. Remember, ‘Search’ is your friend.
If you wish to become PM (Private Message) capable or to ‘edit’, you need 15 posts. To get those 15 posts quickly, just go to the ‘New members introduce yourself here’ section and welcome enough new members to obtain your needed posts to PM/edit. You can always pm a moderator.
Want to post a picture? Start a new thread or make a post, click ‘edit’, click on the ‘paper clip’ or ‘advanced’ and/or ‘manage attachments’ then ‘choose file’ then ‘upload’ and ‘submit’! If Iphone pics, you need to rename any additional pics as Iphone names its pics all the same, image.jpg.
Want to ‘like’ or thank’ someone’s comments? Use the ‘like’ button to the right or the ‘Thanks’ button, bottom right of any post you like. This saves you having to comment.
New members should be aware that the 'New Posts' link next to the 'Search' link top right of the info bar is a great way to see all of the posts you have missed since you were on the forum last. Remember to click 'mark forums read' under ‘quick links’ when you leave.
FREE!! Post your vin in the Vehicle Datacard Request section to get a free datacard (options on your car). You must update your profile with vehicle info and your location and post an introduction first.
http://www.slkworld.com/vehicle-data-card/67706-free-how-get-free-datacard.html

Thank you
Jeff
Moderator/Founding Member/Ride of the Month Coordinator

 

[Wiggy47]

Replaced K40 Relay and problem solved!

Hi All,

I joined the SLK Forum because we were having the "lights on, fast engine fan but no starter motor when ignition key turned" intermittent fault on my wife's 2000 SLK 230. Having read all of the very informative posts here I decided to buy a new K40 relay from MB main dealer. The cost was £153.59 and thanks to Bazzle and others advice I installed it in about 5 mins virtually plug and play. The car seems to run better but maybe thats my imagination! But so far no starting problems!

Just like to say a big thanks to everyone,

Wiggy47

 

[mrg2065]

1999 slk230 k40 repaired 3rd solder joint, top left side, but when I probe the 2nd [middle] and 3rd solder joints I get continuity, is that right? No flow of solder into one another.
Bad solder joint was severely burnt where as the green coating melted and exposed copper.

1999 slk230 k40 repaired 3rd solder joint, top left side, but when I probe the 2nd [middle] and 3rd solder joints I get continuity, is that right? No flow of solder into one another.
Bad solder joint was severely burnt where as the green coating melted and exposed copper.

Continuity beep, worried about hooking back up and starting car, is there supposed to be continuity between the two joints? Thanks again
Mario

 

[Padgett]

Just for S&G, here is the RCM chart from the group-who-must-not-be-named:

•Car will start and run with bad traction control relay. Wing will be up and ABS/ESP lights will be on, possible no speedo operation.
•Car will crank but not start with bad fuel relay (really!).
•Car will not crank or start with bad engine control relay. With key in the ON position, wait, the radiator fan will spin VERY fast.
•Car will start and run with bad air pump relay but will throw a CEL and PO410 code.
•Car will start and run with a bad horn relay. Horn will not work!

 

[leww82]

So i have some electroni knowledege and i was not happy with the engine running! No no codes on the ECu. I took out the K4D (no K40) and i look at the solders via a microscop. I did find out that the solders are bad redo them and now the engine runs like a charm. So my advice is : before maf and coils and all the expensive stuff chek yout solder on the K4D (K40) rel. It is a 5 min job.

 

[lowmoorfarm]

My 230 developed a starting problem but unlike most in this thread it did actually crank over. It would turn over but not start, so with the excellent info I read on here I decided to buy a used K40 from a breaker. Fitted the part and to my disappointment it refused to crank over, and like others on here had the cooling fan running fast too !... Took it apart and manually worked all the relays and refitted. It now starts and runs a treat with no bother..


Thanks guys for all the great info on here, it really helped get me sorted. I'm now going to buy another K40 as a spare just in case.

 

[Healey]

Hi
This is a very interesting thread, but I am confused and I wonder if someone could clarify.


Do the symptoms and fixes mentioned in this thread apply to the Facelift R170 (Year 2000 onwards) or is it ONLY the Non Facelift version.(before Year 2000)


I ask this because the layout is different and therefore I guess the K40 Relay module is different ? is that correct ?


Thanks

 

[efair]

Good question; my gut is it applies to both.

 

[Padgett]

Can say it is common in Crossfires also (SLK320 made through 2008).