Mercedes A140 central lock pump control board repair

[ignislion]

Hello!

I am in a quest to help to restore my friend's car. Many were done but the last thing remaining is pneumatic locking.

I have break out the board and make some testings , as for me it looks like the controller is dead because everything else by itself is working well.

To test the controller, I have tried both to apply ground do 3rd contact on the connector and directly to the controller's leg. And sometimes it just works, it looks like I am not doing anything special, in another try motor just starts, and then not.

The controller on the board is a https://www.nxp.com/docs/en/data-sheet/MC68HC05K1.pdf so there is absolutely no chance to get and program a new one. The controller and nearest components are looking good. Only two things to consider: the reset pin was corroded a bit, but I have soldered it and now it looks good, and another thing is an oscillator, manual says it must be run on 2 MHz in this configuration but I have measured only 1. Not sure how much it worth attention.

But it may be that I am doing it wrong because the board can actuate fuel flap separate from doors locks, using an onboard solenoid valve. And this is done by 1 signal line. So there must be some protocol, at least more than just the HI\LO line. But I have failed to find any information about it and any information about. So maybe someone could know definitely how it is done or at least where to dig?

And another thing which I think may cause magick is sleep modes. It is said that the controller has 2 types of those. WAIT is a probable one but I have failed to reproduce awakening so I decided it is not the truth. But on the IRQ pin, there is some strange greeny boxy sensor type thing, I have an idea that it is an impact sensor, but can not be sure. Maybe someone can help with this too?

https://oshwlab.com/wbnerd/w168_board

Thank You for attention!

[esepecesito]

Take a look at SENT and LIN protocols
https://en.wikipedia.org/wiki/SENT_(protocol)
https://en.wikipedia.org/wiki/Local_Interconnect_Network
Both are used in automotive for 1 line data.

For that application I would say SENT is more probable.

[Rasz]

>the reset pin was corroded a bit, but I have soldered it and now it looks good

is that picture "looks good" ? you need to desolder it and clean it completely. I would also touch up pins for all the heavy elements on the board. Also clean flux after you solder stuff back on.

[ignislion]

No, images were done at very begining, all suspicious elements were fixed later. Sorry for misinfirmation.

[minifloat]

Hi,

The middle pin of the connector seems to have a weak solder joint. I could see a ring-shaped crack in the solder joint when zooming in (see un-numbered pic).
Same as for at least one of the contacts of the crash sensor (numbered pic 1, 2).
From your textual description I understand you cleaned the poor-looking trace and solder joints (numbered pic 3).

Maybe there might also be other solder joints. I'd inspect them all whilst trying to gently wiggle the components, so solder cracks become more obvious.

Hope this helps you,
br, mf

[YetAnotherTechie]

Have you tested on the car? the center pin is most likely a serial comunication pin, not a on/off contact. what generation a140 is it?

[ignislion]

Just to clarify all concerns about solder joints condition I have made a new photo(as good as I managed). And I have tested all suspicious connections for leaks and have a couple of runs "emulating" controller behavior with kinda like a jig.

Currently, I'm waiting for a moment to take a whole car for the test(maybe in a week or so) with "DSlogic" to try to sniff protocol. It seems like LIN is very plausible, it was extensively used by Mercedes right at the time of the development of W168.

Still this piece of textolite =)

Thank you, guys!

BTW maybe someone knows where to read about a good and cheap way to photo boards? I felt shy posting those blurry glary photos  =)

[ignislion]

Currently, I do not have VIN in my hands, so I can't tell precisely but it is W168 made in 1998.

The central pin is +12V I know it for sure.

I have tested the whole assembly on the car right after resoldering and it behaves just like before, on the power-up it closes all doors by "generating vacuum" and then stops to react to any actions.
I sure that the control line works at least in some way, by measuring it with a voltmeter, there was something going on, so buttons and keys are working. How is it working exactly, and is it in good health I will discover in a couple of days.

[perieanuo]

look in pic attached: you really gotta resolder ALL, takes 20 min
you miss spots, so it's not ok
after eliminating those basic connection problems, clean (but really clean the board, with acetone - be careful not to damage plastic parts of course, dry the pcb)
that pin corrosion need to be correctly resolved. better, remove chip/clean and replace it.
after this, we can discuss

[fzabkar]

Depending on the PCB, I use a CCD scanner (not CIS) to get high quality, hires photos.

Otherwise ...

https://www.ifixit.com/Guide/How+to+Take+Awesome+Photos/38496

[meu]

Hi, I've a somehow similar problem in an A160. Pump doesn't work, but sometimes it does if I'm manipulating or taping it.
I've been trying to power the pump directly to check if always work,  but I doesn't know how to do that.
I was following this other thread: https://www.benzworld.org/threads/central-locking-a-different-kind-of-problem.2611321/ where they was also trying to dig how to force run. According them, naming the pings 4,5,6 in this shape:[-|-|-|4|5|6], they say that 5 corresponds to +12v permanent and 6 to ground, being the 4 the unknown.

Have you been able to get any progress or being able to check parts from outside the car?

[Squoip]

I still see a couple of dodgy looking solder joints. That looks like a single sided PCB and they are notorious for fractured solder joints. I second the opinion that you should re-solder every connection on the board but wouldn't suggest acetone for cleaning for multiple reasons. I always use 99% IPA which is what we used when I was in manufacturing. Also I would recommend you use liquid flux if you have or can obtain some.

[SilverSolder]

[...]

BTW maybe someone knows where to read about a good and cheap way to photo boards? I felt shy posting those blurry glary photos  =)

Photography is all about the light...   Cheapest option is to take your board pictures on an overcast day (shadow free light), either outside or by a window.

[ignislion]

I have viewed one of Dave's Videos exactly about doing photos of small objects. And have created this pile of paper =) But it works perfectly it is too sad that I currently have no reason to shoot something =)

[ignislion]

A couple of months ago we finally had time to settle this thing, we borrow a garage from a friend of mine. So I take my DSO to define which protocol this thing uses. But the signal was so distorted that there is no doubt what was a problem. We ruined half a car to find a place where the wiring was damaged, repaired it with copper sleeve and tape and the pump starts to work. I even don't bother myself with any further details of how this thingy works 

Thank you for your help!