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K40 fix

16K views 45 replies 8 participants last post by  mrg2065 
#1 ·
Hello, 1999 slk230 k40, cleans and
repaired 3rd solder joint, top left side k40 relay, but when I probe the 2nd [middle] and 3rd solder joints with multimeter I get continuity, is that right? No flow of solder into one another.
Bad solder joint was so severely burnt where as the green coating melted and exposed copper. Worried about hooking back up and starting car, if there's not supposed to be continuity, anyone have a k40 out and multimeter to check for me.
Thanks,
Mario
 

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#4 ·
Apologies @mrg2065 - not seen your post.

Your picture isn't the clearest so I can't see exactly where you are referring to on the K40. I have a wiring diagram of the unit that may help you but I can't add it successfully to the forum directly as it get reduced in size (click on the thumbnail and you will see what I mean). Currently you can't PM me as you do not have enough posts under your belt, but you can PM @Avel Du with your email address and he can pass it on to me. I can then email you the full resolution diagram. This should help you test the connections you are seeing.

Do be aware that some pins on the K40 have diodes between them: these will typically measure a low resistance one way and a high resistance the other, so you may be seeing something like this with your measurements. Others pins have resistors, relay coils or closed relay contacts across them and these too may give unexpected readings depending on what range you have the multimeter set to during your tests. It's difficult to know without more detail from your situation.

Cheers

 

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#6 ·
Apologies @mrg2065 - not seen your post.

Your picture isn't the clearest so I can't see exactly where you are referring to on the K40. I have a wiring diagram of the unit that may help you but I can't add it successfully to the forum directly as it get reduced in size (click on the thumbnail and you will see what I mean). Currently you can't PM me as you do not have enough posts under your belt, but you can PM @Avel Du with your email address and he can pass it on to me. I can then email you the full resolution diagram. This should help you test the connections you are seeing.

Do be aware that some pins on the K40 have diodes between them: these will typically measure a low resistance one way and a high resistance the other, so you may be seeing something like this with your measurements. Others pins have resistors, relay coils or closed relay contacts across them and these too may give unexpected readings depending on what range you have the multimeter set to during your tests. It's difficult to know without more detail from your situation.

Cheers

Happy to be intermediary.

@mrg2065 You could go and welcome 5 new members.
20-30 mins later you will be PM active.

Mods can be PM'd by anyone at any time regardless of post count.
Thanks again for your help, yes when I pull F3 fuse there's no continuity, seen another post regarding recirculating air flap relearning process is that done on this SLK model? Holding flap open 90deg, 15 sec, key on, then 45 sec, something like that, I got procedure saved if so.
Thanks again.
Mario
 
#11 · (Edited)
Alright Thanks all for the help, plugged K40 in started SLK and recirculating air flap is working, pump feels/sounds stronger, check engine light off. should pass emissions now after Recirculating air flap harness repaired and k40 joints re-soldered.
Failed Emissions in 2014 with same codes.P1235, P1236, and P1525, miss placed this years exact same test results, side mechanic at emissions testing sight here in Seattle, Wa. must of cut SC harness tan or beige wire, showed effort on the paperwork and gave SLK a Pass to get the tabs in 2014, then I re soldered a yellow wire to pin I popped out of harness and with you guys and a forum topic search on codes found the Problem and corrected it.
Thank you!!

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#12 ·
New o2 sensor, getting a pending p0135, o2 sensor heater circuit. So i cut old harness off Old o2 and pluged in and probed wires for grounding, i am getting readings when grounded to grey wire, and also one of the white wires. On harness grey wire plugs in to black ground, and white wire plugs in to a black/white striped, which goes right into area on k40 repaired area The board in area was severely burned, think it was un repairable, hence the p0135,
Unless the bk/w striped is also continuously grounded, haven't probed with key on. Thoughts?
 

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#13 · (Edited)
Ahhh probably a pispoor solder job, got a jewelers eye scope, middle joints need touch up, hit a couple other joints, and going to clean off crappy area i soldered and properly clean and resolder,
Will order new K40 just in case.
Correction o2 wires go to opposite end of repaired area, resoldered those joints as well.
 
#15 ·
Out of interest, @mrg2065 what soldering iron are you using? I only ask because there is a lot of metal around these joints and the relays/pins that you have to heat to a good enough temperature to melt solder. If your iron is too small (like a 15W hobby iron) then it will take forever to get the energy into the joint to properly melt and flow the solder. You should have a decent 25W or 50W iron with a clean bit and plenty of solder in a reel to properly tin, heat and flow the joint.
 
#23 ·
Thanks in post 12 i mentioned the recirculating air flap was working after repair, if that's the valve your talking about, i pulled the k40 last night,(didn't reset ecu) to look over, plugged it in this morning to run to work and the cel was off for a few miles then came back on, get some good electical cleaner and try soldering again while waiting for payday,
Stupid me didn't properly clean, hope i didn't mess it up.
 
#27 ·
Going to buy a new k40, this one looks to fried. Any recommendations on where to buy one, Rock Auto, someone you bought off Ebay, will replace electronic air intake chang over valve and whatever other valves to do with secondary air injection,and also coils, and MAF. Want to order tomorrow if possible.
Thanks to all for the previous help and looking.
 
#31 · (Edited)
There's power on one of the o2 heater white circuit wires, key on engine off,
and 12.06 v on multimeter black ground wire to pos terminal, key off.
No ohms touching two white wires, multimeter set at 200 ohms on car. No ohms on the old o2 off car either. Took off new O2 sending back and getting warranty replacement and try again.
 
#32 ·
Think I found the problem, image of old harness, and new harness, one white wire pin only half is there, probed it and got 12.3 ohms, well minutes ago I did, tried again and 0 ohms. Defective: I guess the malfunction reading was the loose connection, seem tiny metal shavings fall out.
 

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#36 ·
Kool thanks, thinking of getting a book, got a subscription with alldata for the slk.
Not just any - check the packaging for "O2 safe". The threads might need chasing based on the galling I see in your photo.
I just slapped it on and torqued it to 26 ft lbs. No codes popping up, just got to do the drive cycle, dealing with a faulty thermostat, and flushing system now.
Thanks
 
#37 ·
Ok working on cooling system now, but when I raise the RPM's still here a chirp towards the back of engine, no codes popping up since new k40, o2 and maf, seen this little hole in the back of intake(?), is that a bleed hole to let you know there's a leak inside? Haven't checked the hole, just seen it today, waiting to get MB coolant, before I can start engine to check
Thanks again.
 

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#38 ·
Yea got to be a bleed hole for some kind of my guess oil getting through where it shouldn't, or air, maybe, seems a little low, not an MB tech.
Anyone know if maybe a "chirp" does come out that little hole when revving, in the picture posted previously?
Thanks Mario

Calling All Pro's
 
#40 ·
All I can tell you is mine had a broken pin on the pigtail going into, recirculating air flap, soldered busted pin and yellow wire, (originally tan)together, and flap worked, forget if it was stuck open or closed.
I didn't diagnose the problem, just asked about a new pigtail on an emissions side mechanic report.
 

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